Prayer Time Calculator Version 2.5 Program and documentation by Dr. Monzur Ahmed Released 20th February 1995 'As to those who hold fast by the Book and establish regular prayer,- never shall We suffer the reward of the righteous to perish.' (Al-Qur'an 7:17) ----------------------------------------------------------------------------- CONTENTS ----------------------------------------------------------------------------- 1. INTRODUCTION 2. GETTING STARTED 2.1 System Requirements 2.2 Files on Disc 2.3 Making Backups 2.4 Running PTC on a floppy drive system 2.5 Installing and running PTC on a hard drive system 3. USING THE COMPUTER PROGRAM 3.1 OPTION 1: CALCULATE PRAYER TIMES FOR A DAY 3.2 OPTION 2: CALCULATE PRAYER TIMES FOR A MONTH 3.3 OPTION 3: DRAW GRAPH OF PRAYER TIMES VERSUS DATE 3.4 OPTION 4: QIBLA DIRECTION 3.5 OPTION 5: ADD/DELETE/CHANGE/VIEW ATLAS DATA 3.5.1 Add data 3.5.2 Delete data 3.5.3 Change data 3.5.4 View data 3.6 OPTION 6: CHANGE/VIEW DEFAULTS 3.6.1 Default City 3.6.2 Default Year 3.6.3 Which Asr time(s) to be displayed 3.6.4 Which Fajr and Isha time(s) to be displayed 3.6.5 Twilight angle 3.6.6 Start and End of Summer Time/Daylight Saving Time 3.6.7 Monitor Type 3.6.8 Custom Line 3.7 OPTION 7: INFORMATION ON TWILIGHT 4. TECHNICAL INFORMATION 4.1 Definitions of Prayer Times 4.2 Persisting Twilight 4.3 Mathematical Equations for Prayer Times 4.4 Qibla Direction 4.5 Shortest Distance to Makkah 5. SHAREWARE/CHARITYWARE 6. FUTURE DEVELOPMENTS 7. CONCLUSION 8. REFERENCES ----------------------------------------------------------------------------- 1. INTRODUCTION ----------------------------------------------------------------------------- The five Islamic prayers are named Fajr, Zuhr, Asr, Maghrib and Isha. The timing of these five prayers varies from place to place and from day to day. It is obligatory for Muslims to perform these prayers at the correct time. The prayer times for any given location on earth may be determined mathematically if the latitude and longitude of the location are known. However, the theoretical determination of prayer times is a complex process and would normally be impractical even with the aid of a pocket calculator. Much of this tedium may be alleviated by using computers. This computer program was developed to allow the non-specialist to calculate prayer times accurately for any city in the world. The program is menu driven and allows the user to simply enter the name of a city and the date to obtain the prayer times for that city. Prayer times for a single day or for a whole month may be obtained and can be printed out or saved to disc for future reference. If your computer supports graphics, a graph can be obtained showing how the prayer times vary throughout the year for a given location. British Summer Time and Daylight Saving Time (DST) can be automatically compensated for. In addition to calculating prayer times, the program also calculates the Qibla direction from any location and the distance of that location from Makkah using spherical trigonometry. The program is able to draw world maps (spherical and flat projections) showing the position of your location relative to Makkah. The program has a built in atlas database which can store the longitude and latitude data of upto 1000 cities. If a certain city is not already in the database, it may be easily added. ----------------------------------------------------------------------------- 2. GETTING STARTED ----------------------------------------------------------------------------- 2.1 System Requirements ======================= Prayer Time Calculator (PTC) will work on all PC XT and AT computers and compatibles equipped with at least one floppy drive and 512K of memory. A hard drive is preferable. To obtain graphics you will need one of the following graphics adapters: CGA, EGA, VGA or Hercules. VGA gives the best results. If you do not have graphics, then don't worry - you will still be able to obtain displays of tables showing prayer times and Qibla direction. 2.2 Files on Disc ================= The following files should be present on your distribution disc: PT25.EXE The main program DATA.PTC Contains data for the built in atlas database DEFAULTS.PTC Contains the initial default settings WORLDMAP.PTC Contains data to generate map README.TXT This file! WHATSNEW.TXT Enhancements since last release Only PT25.EXE is absolutely necessary for the program to function. Even if DATA.PTC, DEFAULTS.PTC and WORLDMAP.PTC are missing, the program will still run, although sub-optimally. 2.3 Making Backups ================== As with all new programs, it is advisable to make backup copies of all the files. You should then write protect the original disc and keep it in a safe place. Use only the backed up disc. 2.4 Running PTC on a floppy drive system ======================================== Place your disc in, say, drive A. Now make sure you have the A:> prompt showing: A:> Type PT25 and the program will commence. If you wish to save data to the disc ensure that the disc is not write- protected. 2.5 Installing and running PTC on a hard drive system ===================================================== Let us assume that your hard drive is called drive C. You should initially make a directory called e.g. PTIME: md c:\ptime Put the floppy disc containing the program into drive A. Copy all the files from the floppy disc into the PTIME directory: copy a:*.* c:\ptime Ensure that you are logged onto the PTIME directory (IMPORTANT!): cd c:\ptime Now type PT25 and the program will commence. [Technical Note: the program searches the current directory for DATA.PTC, DEFAULTS.PTC and WORLDMAP.PTC. It is therefore important that you are logged onto the PTIME directory (by typing cd c:\ptime) before running the program.] ----------------------------------------------------------------------------- 3. USING THE COMPUTER PROGRAM ----------------------------------------------------------------------------- The program allows the user to chose a city from the built in database or a new city may be entered. The prayer time for either a single day or a whole month may be tabulated. A graph may be drawn showing how the five prayer times vary throughout the year for a given city. In addition, the Qibla direction and distance to Makkah may be displayed. When the program is started, you will be presented with a menu: IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I Prayer Time Calculator Version 2.5 I I By Dr. Monzur Ahmed (c) Nov 88/Feb 95 I I I I----------------------------------------------I I M A I N M E N U I I----------------------------------------------I I I I 1. Calculate Prayer Times for one DAY I I 2. Calculate Prayer Times for one MONTH I I 3. Graph of Prayer Times vs Date I I 4. Qibla Direction I I 5. Add/ Delete/ Change/ View Atlas Data I I 6. Change/ View Defaults I I 7. Information on Twilight I I X. Exit to DOS I I I I Use cursor keys or 1-7 to make choice I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII You may make a choice from this menu either by using the cursor keys to highlight the desired option and pressing enter or by pressing 1,2,3,4,5,6,7 or X directly. 3.1 OPTION 1: CALCULATE PRAYER TIMES FOR A DAY =============================================== When this option is chosen (and options 2, 3 and 4), the following screen will appear: IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIII ICurrent Place = BIRMINGHAM I I ABERDEEN I IPress ENTER to accept or type in new place I I ACCRA I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I ALGIERS I I AMSTERDAM I NAME OF PLACE ? I ANKARA I I ATHENS I I BAGHDAD I I BANGKOK I I BELFAST I I BERLIN I I BERNE I I BIRMINGHAM << I I BOGOTA I I BONN I I BRADFORD I I BRASILIA I I BRUSSELS I IIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIII I CURSORS & PAGE UP/DN I I to move pointer I IIIIIIIIIIIIIIIIIIIIIIIIII Initially, the location has to be entered. The program comes with a built in database of about 100 cities (you can add to or modify this database, see section 3.5). The places that are already in the database are listed in a scrolling window on the right. You can choose a place from the database either by highlighting it with the cursor keys and pressing ENTER or by typing the name of the place and pressing ENTER. If you type in the name of a place which is not in the database, the program will ask you to enter the latitude, longitude, reference longitude and height above sea level of this place. You will also be asked *if* Summer Time operates at this location. (Note that the rules determining *when* Summer Time starts and ends can be altered using 'Option 6. Change/View Defaults' from the Main Menu; see below). The latitude and longitude should be available from a world atlas. The reference longitude is the time zone of the place multiplied by 15 (e.g. if the time zone is +3 hours then the reference longitude is 15*3= 45E; if the time zone is -7 hours then reference longitude= 15*-7=105W; note East is positive, West is negative). Next, the year, month and date are entered. The computer then calculates the prayer times. The results may be sent to a printer, to the disc (as an ASCII file) or just to the screen, for example: ================================================================= Start of prayer times at BIRMINGHAM on Thu 1 December 1994 :- Fajr (1/7 rule)........ 5:32 Fajr................... 5:49 Sunrise................ 7:46 Zawal..................11:56 Asr [1]................13:44 Asr [2]................14:16 Maghrib/Sunset.........16:07 Isha...................18:04 Isha (1/7 rule)........18:21 ================================================================= Latitude 51:30N Longitude 1:55W Height ASL: 236m Reference longitude 0:00 Twilight angle: 18 degrees ================================================================= Press SPACE BAR to return to main menu... ************************************************************************** ** Generally speaking, pressing ESC during the program will either skip ** ** questions (accepting the last set of inputs or defaults) or return ** ** you to the Main Menu. ** ************************************************************************** 3.2 OPTION 2: CALCULATE PRAYER TIMES FOR A MONTH ================================================= Again a city is chosen from the database or entered manually as described above. Next the year and month are entered. A table of prayer times for the month is automatically generated and may be sent to a printer, to the disc (as an ASCII file) or just to the screen. If the table is sent to the disc or printer, the user is allowed to add a custom line which will appear at the head of the table. A typical printout is shown below: In the name of Allah the Beneficent the Merciful ======================================================= BIRMINGHAM 51:30N 1:55W MARCH 1995 Reference Longitude 0:00 Time zone: 0.0 hrs Twilight angle: 18 degrees Height ASL: 236m Summer Time: starts 26/3/1995 finishes 22/10/1995 ======================================================= Date Day Fajr Sunrise Zawal Asr[2] Maghrib Isha ======================================================= 1 Wed 5:04 6:51 12:20 15:53 17:49 19:37 2 Thu 5:02 6:49 12:20 15:55 17:51 19:39 3 Fri 4:59 6:47 12:20 15:56 17:53 19:40 4 Sat 4:57 6:45 12:20 15:58 17:55 19:42 5 Sun 4:55 6:43 12:19 16:00 17:56 19:44 6 Mon 4:53 6:40 12:19 16:01 17:58 19:46 7 Tue 4:50 6:38 12:19 16:03 18:00 19:47 8 Wed 4:48 6:36 12:19 16:04 18:01 19:49 9 Thu 4:46 6:34 12:18 16:06 18:03 19:51 10 Fri 4:43 6:31 12:18 16:07 18:05 19:53 11 Sat 4:41 6:29 12:18 16:08 18:07 19:55 12 Sun 4:39 6:27 12:18 16:10 18:08 19:57 13 Mon 4:36 6:25 12:17 16:11 18:10 19:59 14 Tue 4:34 6:22 12:17 16:13 18:12 20:00 15 Wed 4:31 6:20 12:17 16:14 18:14 20:02 16 Thu 4:29 6:18 12:17 16:16 18:15 20:04 17 Fri 4:26 6:16 12:16 16:17 18:17 20:06 18 Sat 4:24 6:13 12:16 16:18 18:19 20:08 19 Sun 4:21 6:11 12:16 16:20 18:20 20:10 20 Mon 4:19 6:09 12:15 16:21 18:22 20:12 21 Tue 4:16 6:07 12:15 16:22 18:24 20:14 22 Wed 4:14 6:04 12:15 16:24 18:25 20:16 23 Thu 4:11 6:02 12:15 16:25 18:27 20:18 24 Fri 4:08 6:00 12:14 16:26 18:29 20:20 25 Sat 4:06 5:57 12:14 16:28 18:30 20:22 26* Sun 5:03 6:55 13:14 17:29 19:32 21:24 27* Mon 5:00 6:53 13:13 17:30 19:34 21:26 28* Tue 4:58 6:51 13:13 17:32 19:36 21:28 29* Wed 4:55 6:48 13:13 17:33 19:37 21:30 30* Thu 4:52 6:46 13:12 17:34 19:39 21:33 31* Fri 4:50 6:44 13:12 17:35 19:41 21:35 ======================================================= NOTES: Height ASL: height above sea level in metres Reference Longitude: Time Zone x15 Zawal: Midday - should not pray 5 mins before or after Asr[2]: Asr Hanafi (shadow = 2x object) * : one hour added for Summer Time ======================================================= Data from Prayer Time Calculator Version 2.5 By Dr. Monzur Ahmed, Birmingham, UK. Feb 1995 ======================================================= The number of columns displayed in the table may be altered by the user (see section 3.6). Another example of a table displaying all the possible columns is shown below: You can put a Mosque Name on this line ============================================================================== BIRMINGHAM 51:30N 1:55W MAY 1995 Reference Longitude 0:00 Time zone: 0.0 hrs Twilight angle: 18 degrees Height ASL: 236m Summer Time: starts 26/3/1995 finishes 22/10/1995 ============================================================================== Date Day Fajr/7 Fajr Sunrise Zawal Asr[1] Asr[2] Maghrib Isha Isha/7 ============================================================================== 1* Mon 4:19 3:13 5:37 13:05 17:07 18:10 20:33 22:57 21:50 2* Tue 4:18 3:10 5:35 13:05 17:07 18:11 20:34 23:00 21:51 3* Wed 4:17 3:06 5:33 13:05 17:08 18:12 20:36 23:03 21:53 4* Thu 4:15 3:02 5:32 13:05 17:09 18:13 20:37 23:07 21:54 5* Fri 4:14 2:59 5:30 13:04 17:09 18:14 20:39 23:10 21:55 6* Sat 4:13 2:55 5:28 13:04 17:10 18:15 20:41 23:14 21:56 7* Sun 4:11 2:51 5:26 13:04 17:11 18:16 20:42 23:17 21:57 8* Mon 4:10 2:47 5:24 13:04 17:11 18:17 20:44 23:21 21:58 9* Tue 4:09 2:43 5:23 13:04 17:12 18:18 20:46 23:25 21:59 10* Wed 4:08 2:39 5:21 13:04 17:13 18:19 20:47 23:29 22:01 11* Thu 4:06 2:35 5:19 13:04 17:13 18:20 20:49 23:33 22:02 12* Fri 4:05 2:31 5:18 13:04 17:14 18:21 20:50 23:37 22:03 13* Sat 4:04 2:26 5:16 13:04 17:14 18:22 20:52 23:42 22:04 14* Sun 4:03 2:22 5:14 13:04 17:15 18:23 20:54 23:46 22:05 15* Mon 4:02 2:17 5:13 13:04 17:16 18:24 20:55 23:51 22:06 16* Tue 4:01 2:12 5:11 13:04 17:16 18:25 20:57 23:56 22:07 17* Wed 4:00 2:07 5:10 13:04 17:17 18:26 20:58 0:01 22:08 18* Thu 3:59 2:01 5:08 13:04 17:17 18:26 21:00 0:07 22:09 19* Fri 3:58 1:55 5:07 13:04 17:18 18:27 21:01 0:13 22:11 20* Sat 3:57 1:49 5:06 13:04 17:18 18:28 21:03 0:20 22:12 21* Sun 3:56 1:41 5:04 13:04 17:19 18:29 21:04 0:27 22:13 22* Mon 3:55 1:32 5:03 13:04 17:20 18:30 21:05 0:37 22:14 23* Tue 3:54 1:17 5:02 13:04 17:20 18:31 21:07 0:51 22:15 24* Wed 3:53 ?? 5:01 13:04 17:21 18:31 21:08 ?? 22:16 25* Thu 3:52 ?? 4:59 13:04 17:21 18:32 21:10 ?? 22:17 26* Fri 3:51 ?? 4:58 13:05 17:22 18:33 21:11 ?? 22:18 27* Sat 3:51 ?? 4:57 13:05 17:22 18:34 21:12 ?? 22:19 28* Sun 3:50 ?? 4:56 13:05 17:23 18:35 21:13 ?? 22:20 29* Mon 3:49 ?? 4:55 13:05 17:23 18:35 21:15 ?? 22:20 30* Tue 3:49 ?? 4:54 13:05 17:24 18:36 21:16 ?? 22:21 31* Wed 3:48 ?? 4:53 13:05 17:24 18:37 21:17 ?? 22:22 ============================================================================== NOTES: Height ASL: height above sea level in metres Reference Longitude: Time Zone x15 Fajr/7: Fajr time using 1/7th night rule Zawal: Midday - should not pray 5 mins before or after Asr[1]: Asr Shafi (shadow = 1x object) Asr[2]: Asr Hanafi (shadow = 2x object) Isha/7: Isha time using 1/7th night rule * : one hour added for Summer Time ?? : twilight persists between sunset and sunrise ============================================================================== Data from Prayer Time Calculator Version 2.5 By Dr. Monzur Ahmed, Birmingham, UK. Feb 1995 ============================================================================== Note how in Birmingham, UK, for the latter half of May the program is unable to calculate 'normal' Fajr and Isha (indicated by ??) because twilight persists between sunset and next sunrise. Under these circumstances the times in the Fajr/7 and Isha/7 columns may be used. Fajr/7 and Isha/7 are calculated using the 1/7th night rule (see section 4. Technical Notes). In the above table, both Asr Shafi and Asr Hanafi are displayed. 3.3 OPTION 3: DRAW GRAPH OF PRAYER TIMES VERSUS DATE ===================================================== A city is chosen from the list or entered manually. If your computer supports graphics, a graph will then be drawn on the screen showing how the prayer times vary throughout the year. The vertical axis represents the time of day (not taking into account Summer Time/DST) while the horizontal axis represents the month of the year. There will be upto nine curves (depending on the default settings) labelled as follows: F7 = fajr using 1/7th night rule F = fajr (normal) SR = sunrise Z = zawal A1 = asr (length of shadow = length of object) A2 = asr (length of shadow = 2 x length of object) M = maghrib/sunset I = isha (normal) I7 = isha using 1/7th night rule The graph may be printed out on an EPSON compatible dot matrix printer or a HP Laserjet/Deskjet printer by pressing P and following the prompts. (NOTE To abort whilst a graph is being drawn, press ESC). The display may be converted to black and white by pressing B. The latter option is useful if one wishes to 'grab' the image under Microsoft Windows (by pressing Print Screen in enhanced mode) for inclusion in a wordprocessor document. 3.4 OPTION 4: QIBLA DIRECTION ============================== This option calculates and displays the Qibla direction from a location and the shortest distance to Makkah from that location. The location is chosen in the usual manner as described above. The program gives the option of displaying the result in either TEXT or GRAPHICS mode. TEXT mode is recommended for users with slow computers (less than a 386 processor). In TEXT mode the result is shown as a simple table: ====================================================== BIRMINGHAM 51:30N 1:55W ====================================================== Qibla Direction (Bearing from North) 117:02 Distance to Makkah 3044 statute miles (4899 km) 2645 nautical miles ====================================================== In GRAPHICS mode, a world map is drawn showing the position of your location relative to Makkah. The default is a spherical projection for the map with your location at the centre. The GRAPHICS mode may be slow for users with low-powered computers. Several options are available once the map is drawn: P: printout of map (Epson compatible dot matrix or HP Laserjet/Deskjet) S: toggles between a flat and spherical map G: toggles between 'glass' and opaque sphere Cursors: spin and tilt sphere in 4 directions C: puts your location back in the centre L: toggles your city and Makkah labels on/off N: removes tilt on sphere Note that the Qibla direction and shortest distance to Makkah are calculated using spherical trigonometry. The Qibla direction depends on the 'great circle of navigation' which goes through Makkah and your location. The Qibla direction is given as the bearing of Makkah from geographic North i.e. degrees clockwise from geographic north. The geographic north and magnetic north (as determined by a compass) vary depending on location and from year to year. The magnitude of this difference may be obtained from a magnetic atlas (e.g. reference 9). Some of the Qibla angles may seem a little strange. This is because we are used to seeing world maps drawn using the Mercator or 'flat' projection methods. The Mercator projection was designed for navigation along the so called 'Rhumb Line'. Sailing/flying along he Rhumb Line allows the course to be fixed to one angle for the whole journey. The Qibla angle is NOT the direction of a straight line joining your location to Makkah on a 'flat' map. The earth is spherical and the true Qibla direction is calculated using spherical trigonometry (see Technical Notes). For example, in Alaska the true Qibla direction is North and not South-East as a cursory look at a flat map might suggest. If you are still confused, examine a globe (and see reference 5 or 6). 3.5 OPTION 5: ADD/DELETE/CHANGE/VIEW ATLAS DATA ================================================ The program has a built in database which can store data for upto 1000 cities. The program is shipped with about 100 cities already on the database. The following pieces of information are stored for each city: Name of city Country (optional) Latitude Longitude Reference longitude (15 x Time Band) Whether influenced by Summer Time Height above sea level in metres Choosing this option allows us to make alterations to the ATLAS DATABASE: IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I Prayer Time Calculator Version 2.5 I I By Dr. Monzur Ahmed (c) Nov 88/Feb 95 I I I I----------------------------------------------I I A T L A S D A T A B A S E I I----------------------------------------------I I I I I I 1. Add data I I 2. Delete data I I 3. Change data I I 4. View data I I X. Exit to Main Menu I I I I I I I I Use cursor keys or 1-4 to make choice I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII It is best to add a town to the atlas before using it so as to save time inputting latitude/longitude data. 3.5.1. Add data --------------- Follow the prompts and enter the name of the new location, the country (optional), the latitude, longitude and reference longitude (i.e time zone x 15, e.g. if the time zone is +3 hours then the reference longitude is 15*3= 45E; if the time zone is -7 hours then reference longitude= 15*-7=105W). Enter the height of the location above sea level (zero if you do not know) and also *whether* summer time (British Summer Time/ Daylight Saving Time) should operate. (Note that the rules determining *when* Summer Time starts and ends can be altered using 'Option 6. Change/View Defaults' from the Main Menu, see section 3.6.6) Once the location has been entered into the database, it will be saved and the name of the location will appear in the scrolling window when option 1,2, 3 or 4 are chosen from the Main Menu. 3.5.2. Delete data ------------------ Simply type in the name of a location which exists on the database to remove it from the database. Make sure that the spelling is correct (although the case does not matter). 3.5.3. Change data ------------------ Type in the name of a location which already exists on the database and follow the prompts to alter its properties. 3.5.4. View data ---------------- This generates a table showing all the locations stored in the database in alphabetical order. Use Page Up/Down to browse. 3.6 OPTION 6: CHANGE/VIEW DEFAULTS =================================== The following screen is displayed: IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII I I I CURRENT DEFAULT SETTINGS I I I I Default City: BIRMINGHAM I I Default Year: 1995 I I Asr time to be displayed: 3 I I where [1]: shadow = length of object I I [2]: shadow = 2 x length of object I I [3]: both I I Fajr and Isha times to be displayed: 3 I I where [1]: normal I I [2]: 1/7th night rule (Sube Al-Lail) I I [3]: both I I Twilight angle: 18 degrees I I Summer Time, if present, begins on fourth Sunday of month 3 I I ends on fourth Sunday of month 10 I I Monitor Type: Colour I I Custom Line:In the name of Allah the Beneficent the Merciful I I I I Press SPACE BAR to make changes... I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII Pressing the Space Bar allows the user to change the following values which are stored as defaults and remembered when the program is next run: 3.6.1 Default City - usually set to the users home town. ------------------- 3.6.2 Default Year - usually set to the current year. ------------------- 3.6.3 Which Asr time(s) to be displayed ---------------------------------------- Asr1 (length of shadow = length of object), Asr2 (length of shadow = 2x length of object) or both. 3.6.4 Which Fajr and Isha time(s) to be displayed -------------------------------------------------- Normal Fajr and Isha using 1/7 night rule (Sube Al-Lail) or both. 3.6.5 Twilight angle --------------------- Generally the twilight angle should be 18 degrees although the program will allow a value between 10 and 20 degrees. 3.6.6 Start and End of Summer Time/Daylight Saving Time -------------------------------------------------------- The rules for the start and finish of Summer Time or Daylight Saving Time (DST) vary from country to country. For example, in 1986 the effective periods for DST for various countries were as follows (data from reference 8): =========================================================== COUNTRY Effective DST period (dates inclusive) =========================================================== AUSTRALIA 26 OCT 86 - 28 FEB 86 CANADA 27 APR 86 - 25 OCT 86 FRANCE 30 MAR 86 - 27 SEP 86 IRAQ 01 APR 86 - 30 SEP 86 ITALY 30 MAR 86 - 27 SEP 86 JORDAN 04 APR 86 - 02 OCT 86 SPAIN 30 MAR 86 - 27 SEP 86 SYRIA 16 FEB 86 - 18 OCT 86 TURKEY 30 MAR 86 - 27 SEP 86 USA 27 APR 86 - 25 OCT 86 UK 30 MAR 86 - 25 OCT 86 =========================================================== During DST, one hour (in most countries) is added to the standard time. In many countries there are general rules for the start and end of DST. For example, in the UK, DST (British Summer Time) usually starts on the fourth Sunday of March and ends on the fourth Sunday of October. Similarly, in most areas of the USA, DST starts on the last Sunday of April and ends on the last Sunday of October. The DST handling of the program has been designed to be flexible enough to cater for most countries of the world. The start/end of DST can be set either as an *absolute* date e.g. 1st May or in a *relative* way e.g. fourth Sunday of March. Essentially you have to answer 3 questions (following the prompts) to set the start or end of DST: Q1. The month when DST starts or ends. Q2. The day on which DST starts or ends. - for absolute date, choose 'Specific date' for this question. - for relative date, choose a day name e.g. 'Sunday' Q3. The position of the day in the month. - for absolute date, enter the date when you want DST to start/end. - for relative date, enter the position of the day in the month i.e. first, second, third, fourth or last. For example if you want DST to start on the last Sunday of the chosen month, enter 'last' or if you want DST to start on the fourth Sunday, enter 'fourth'. Example 1. If you want DST to start on 1st April, the three questions should be answered as follows: Q1. 4 Q2. Specific date Q3. 1 Example 2. If you want DST to start on the last Sunday of April, the three questions should be answered as follows: Q1. 4 Q2. Sunday Q3. last The program ships with default start/end of DST valid for the UK i.e. DST starts on the fourth Sunday of March and ends on fourth Sunday of October. If the Summer Time/DST rules are different for your location then you must alter the rules using this option. If you specify that Summer Time/DST does not apply for your location then these rules will be ignored. 3.6.7 Monitor Type: Colour or Black & White ------------------- 3.6.8 Custom Line ------------------ This is a line of text, maximum 60 characters in length, which can appear at the top of a table printed out or saved to disc. This feature can be used to customise a printed prayer time table. 3.7 OPTION 7: INFORMATION ON TWILIGHT ====================================== This option produces a screen which provides information on the persistence of twilight at extreme latitudes. A brief summary of the four methods of calculating alternative fajr/isha times is displayed. ----------------------------------------------------------------------------- 4. TECHNICAL INFORMATION ----------------------------------------------------------------------------- 4.1 Definitions of Prayer Times =============================== The five Islamic prayers are termed Fajr, Zuhr, Asr, Maghrib and Isha. Twilight is the period before sunrise and after sunset when the sky is partially illuminated by scattered sunlight. The start of fajr and isha depend on twilight. In astronomy, the twilight period is divided into civil, nautical and astronomical twilight which come to an end when the solar depression is 6, 12, and 18 degrees respectively. For the purpose of calculating fajr and isha times a solar depression of 18 degrees is generally used i.e. astronomical twilight. At extreme latitudes solar depression may not exceed 18 degrees for certain months of the year and hence twilight persists between sunset and next sunrise (see below). * FAJR starts with the dawn or morning twilight. Fajr ends just before sunrise. * ZUHR begins after mid-day when the sun has passed the meridian (i.e. after zawal). For convenience, many published prayer timetables add five minutes to zawal to obtain the start of Zuhr. Zuhr ends at the start of Asr time. * The timing of ASR depends on the length of the shadow cast by an object. According to the Shafi school of jurisprudence, Asr begins when the length of the shadow of an object exceeds the length of the object. According to the Hanafi school of jurisprudence, Asr begins when the length of the shadow exceeds TWICE the length of the object. In both cases, the minimum length of shadow (which occurs when the sun passes the meridian) is subtracted from the length of the shadow before comparing it with the length of the object. * MAGHRIB begins at sunset and ends at the start of isha. * ISHA starts after dusk when the evening twilight disappears. 4.2 Persisting Twilight ======================= At extreme latitudes the twilight may persist between sunset and the next sunrise. Hence there is no true night. Under these circumstances, Fajr and Isha times may be calculated using one of four agreed principles: 1. Nearest latitude (Aqrab Al-Balad) - add the interval between sunset and isha for a location on latitude 48 degrees to the local sunset time to obtain time for local isha. Similarly the interval between fajr and sunrise for a location on latitude 48 degrees is subtracted from local sunrise to obtain local fajr time. 2. Nearest day (Aqrab Al-Ayyam) - use fajr and isha times from the last day when it was possible to calculate these times in the normal way for that location. 3. Middle of night (Nisf Al-Lail) - split interval between sunrise and sunset into two halves. Isha is offered before the midpoint (e.g. 15 minutes before) and fajr is offered after the midpoint. 4. One seventh of night (Sube Al-Lail) - split interval between sunset and sunrise into seven segments. Isha is offered after the first segment and fajr is offered after the sixth segment. The program uses the fourth method (1/7th night rule) to give alternative fajr and isha times for use when the normal times are undefined. These alternative fajr and isha times are provided as a guide only. They should not be regarded as absolute standards. Some users may find that one of the other three alternatives is more suitable for their location. Whichever method is used to calculate alternative Fajr/ Isha times, it is important that the same method is used for both fasting and prayer! The phenomenon of persisting twilight does not occur for locations within the latitude range 48S to 48N (approximately) when a twilight angle of 18 degrees is used. 4.3 Mathematical Equations for Prayer Times =========================================== To calculate the prayer times for a certain place we need to know the latitude (B) and longitude (L) of the location and its reference longitude (R). B and L may be obtained from an atlas and R may be calculated by multiplying 15 by the difference between local time and GMT (i.e. 15 x Time Band). We also need to know two astronomical measures called the declination angle of the sun (D) and the real time-mean time difference, also known as the equation of time (T). Declination is the angular distance between a celestial object and the celestial equator. The Declination and the Right Ascension are used together to give the position of a star with reference to the celestial equator and the vernal equinox respectively. The equation of time is a correction to be added to apparent solar time, as read on a sundial, to obtain mean solar time, as commonly used. This difference is a consequence of the ellipticity and tilt of the Earth's orbit, causing the irregular apparent movement of the Sun across the sky. D and T vary according to the time of year and can be obtained accurately from The Star Almanac or calculated approximately as in this program. The following equations may be used to calculate the prayer times: (R-L) T Z = 12+ ----- + --- ........1 15 60 1 {sin(-0.8333-0.0347(H)^0.5)}-sinD.sinB U= -- arccos -------------------------------------- ........2 15 cosD.cosB 1 -sinG-sinD.sinB V= -- arccos --------------- ........3 15 cosD.cosB 1 sin{arccot(1+tan(B-D)}-sinD.sinB W= -- arccos -------------------------------- ........4 15 cosD.cosB 1 sin{arccot(2+tan(B-D)}-sinD.sinB X= -- arccos -------------------------------- ........5 15 cosD.cosB where B= latitude of place L= longitude of place R= reference longitude (i.e. TIME BAND x 15) H= height above sea level in metres D= declination angle of sun from celestial equator (-ve in southern hemisphere) T= mean time - real time difference, i.e. equation of time G= twilight angle Fajr = Z-V Sunrise = Z-U Zuhr = Z Asr1 (Shafi) = Z+W Asr2 (Hanafi) = Z+X Maghrib/Sunset = Z+U Isha = Z+V The program automatically calculates approximate values for T and D from the date (algorithms not shown here). Zuhr time is calculated using equation 1. The time for sunrise and sunset/ maghrib may be calculated by subtracting or adding 'U'(obtained from equation 2) to the Zuhr time respectively. In calculating sunrise and sunset, the program takes into account the height of the location above sea level (if it has been entered into the database). Fajr and Isha times may be calculated by subtracting or adding 'V' (obtained from equation 3) to the Zuhr time respectively. The term G (twilight angle) in equation 3 is usually set to 18 degrees. For a location with an extreme latitude, days in summer may be so long that twilight persists between sunset and the next sunrise. Under these circumstances, 'V' is undefined and Fajr and Isha have to be determined using agreed principles of fiqh. Version 2.x of the program is able to display 'fajr/7' and 'isha/7' i.e. when there is no 'true night' (twilight persists between sunset and next sunrise) the period between sunset and next sunrise is divided into seven segments. Isha is performed after the first segment and fajr after six segments as described above. The start of Asr time (Shafi) may be obtained by adding 'W' (obtained from equation 4) to Zuhr; Asr time (Hanafi) is calculated by adding 'X' obtained from equation 5) to Zuhr. 4.4 Qibla Direction =================== The Qibla direction may be calculated by using spherical trigonometry. sin(Lm-L) Q = arctan ------------------------------- cos(Bm).tan B - sin B.cos(Lm-L) where Q= Qibla bearing from geographic North Lm= longitude of Makkah L= longitude of place Bm= latitude of Makkah B= latitude of place Although the program allows the latitude and longitude of a location to be entered to the nearest minute, for the purposes of calculating Qibla direction, the reference co-ordinates of Makkah (Kaaba) are stored internally with greater accuracy i.e. 21:25:16 N and 39:49:29.1 E. Note that the Qibla direction is relative to geographic north and not magnetic north (as determined by a compass). Geographic and magnetic norths will vary depending on location. This difference is known as magnetic declination and also changes with time. Information on magnetic declinations for a particular location may be obtained from magnetic atlases (e.g. reference 9). From a practical point of view, geographic north-south may be determined using the time of local solar meridian crossing (zawal). The program automatically calculates and displays zawal. At this time, a vertical rod placed on the ground will cast a shadow along the geographic north-south axis. 4.5 Shortest Distance to Makkah =============================== The shortest distance of a place from Makkah in nautical miles is: Distance = 60*arcos {sin B.sin(Bm) + cos B.cos Bm.cos(Lm-L)} Note: 1 International Nautical Mile = 1.150779 statute miles = 1.852km exactly = 2025 yards approximately 1 Statute Mile = 1760 yards = 1.609km ----------------------------------------------------------------------------- 5. SHAREWARE/CHARITYWARE ----------------------------------------------------------------------------- This program was developed over a period of more than 5 years. You may copy and distribute the program FREELY as long as no alterations are made to the program or documentation and no charge is made (other than a reasonable charge for the media and copying). Please ensure that ALL the files, including documentation, are copied. The copyright for the program and documentation remains with the author. If you find the program useful, then you are requested to make a donation to a charity such as Islamic Relief or Muslim Aid (UK addresses given below): Islamic Relief Muslim Aid 19 Rea Street South PO Box 3 Birmingham B5 6LB London N7 8LR U.K. U.K. Tel 0121 622 6477 Tel 0171 609 4425 ----------------------------------------------------------------------------- 6. FUTURE DEVELOPMENTS ----------------------------------------------------------------------------- Prayer Times Calculator is under constant development. Some possible enhancements for future releases include: *Improved Summer Time/ Daylight Saving Time routines. If the present DST options are not suitable for your location then switch this feature off and manually adjust the times. *Mouse support and perhaps a WIMP environment. *If there is sufficient demand, I may produce a Windows version. *I am also presently working on another program called 'MOON CALCULATOR'. This program provides information relating to the position, phase, age, bright limb angle and visibility of the moon for any given date, time and location on earth. It also gives the time and direction of moonrise and moonset, date/time of astronomical new moon and full moon and predicts the location, date/time and direction of the earliest crescent sighting for a given lunar month (using a variety of sighting criteria). Graphic displays showing the position of the moon on a star chart, the position of the moon in a simulated sky and a close-up of the moon are also provided. World maps showing zones where crescent sightings (using a variety of sighting criteria) are likely are also provided. The program is at an advanced stage of development and is undergoing error testing. ----------------------------------------------------------------------------- 7. CONCLUSION ----------------------------------------------------------------------------- For further information or if you have any suggestions to improve the program, please contact me at the address below. I am grateful to the many people who helped in the development of this program. In particular I should like to thank Shakoor Chugthai for his helpful suggestions and extensive error testing. I should also like to thank Abdul Rahman for making the program generally available through Internet. Any errors or omissions that remain are entirely my own. May Allah forgive us all. Wasalaam. ============================================================================= Dr. Monzur Ahmed BSc(Hons), MBChB, MRCP(UK). 27 Poplar Road, Birmingham, B11 1UH, UK. email: monz@netcom.demon.co.uk 20th February 1995 ============================================================================= ----------------------------------------------------------------------------- 8. REFERENCES ----------------------------------------------------------------------------- 1. Dr Husein Kamaluddin [in Arabic] in The Islamic Researches Magazine, 1397AH, vol 1, No 3, Pub: Presidency of Scientific Researches, Ifta, Call and Guidance (Saudi Arabia). 2. Dr Muhmoud N. Nahas; Determination of Prayer Times, The Muslim, December 1985: 12-14. 3. The Star Almanac for Land Surveyors, London, HMSO. 4. Mufti Rasheed Ahmed Ludhyanvi; Ahsunul Fatawa, 1405 AH, HM Saeed Company Publishers, Pakistan. 5. Dr. Mohammad Ilyas; Astronomy of Islamic Times for the Twenty-first Century, 1989; Mansell, London. 6. Dr. Mohammad Ilyas; A Modern Guide to Astronomical Calculations of Islamic Calendar, Times & Qibla;1984,Berita Publishing Sdn Bhd., Kuala Lumpur, Malaysia 7. Moulana Yakub Qasmi and Tariq Muneer, Prayer Times for United Kingdom & Ireland; 1989, Islamic Research Institute of Britain, Dewsbury, UK. 8. Abdul Lateef Bin Abdul Aziz, Perpetual Prayer Time Table for the Whole World; 1986, Published by Abdul Majeed Qureshi, Karachi, Pakistan. 9. Magnetic Variation (Declination) (Epoch 1990); Map No.42 10th Ed; 1992, World Map, USA Defence Mapping Agency