What this study compares
We calculate 365 dates in 2027 for Karachi, New York, London and Sydney with six presets: ISNA, Karachi, Muslim World League, Moonsighting Committee, Umm al-Qura and Egyptian. This is 8,760 city-method-days. ISNA is the common reference for this study, even in cities where it is not SalahTable's default.
This design asks how much the numerical result changes when the preset changes. It does not rank methods by religious validity, observational accuracy or suitability outside their intended regions.
How to read the numbers
A positive difference means later than ISNA; a negative difference means earlier. The range is the minimum and maximum signed difference over all 365 dates. “Mean absolute” is the average size of the daily difference, ignoring its sign. It is not an error against an official timetable.
Annual Fajr and Isha differences from ISNA
Each row compares a preset with ISNA in the same city on the same dates. ISNA's own difference would be zero, so its rows are omitted. All values are minutes.
| City / time zone | Compared preset | Fajr signed range | Fajr mean absolute | Isha signed range | Isha mean absolute |
|---|---|---|---|---|---|
| Karachi Asia/Karachi | University of Islamic Sciences, Karachi | -17 to -13 | 14.3 | +13 to +17 | 14.2 |
| Karachi Asia/Karachi | Muslim World League | -17 to -13 | 14.3 | +8 to +11 | 9.5 |
| Karachi Asia/Karachi | Moonsighting Committee Worldwide | -17 to -13 | 14.3 | +2 to +14 | 9.7 |
| Karachi Asia/Karachi | Umm al-Qura, Makkah | -20 to -15 | 16.6 | +17 to +28 | 23.7 |
| Karachi Asia/Karachi | Egyptian General Authority of Survey | -25 to -19 | 21.4 | +11 to +14 | 11.8 |
| New York America/New_York | University of Islamic Sciences, Karachi | -27 to -15 | 18.7 | +15 to +27 | 18.7 |
| New York America/New_York | Muslim World League | -27 to -15 | 18.7 | +10 to +18 | 12.4 |
| New York America/New_York | Moonsighting Committee Worldwide | -16 to -8 | 13.5 | -23 to +12 | 10.9 |
| New York America/New_York | Umm al-Qura, Makkah | -32 to -18 | 21.9 | -10 to +16 | 9.8 |
| New York America/New_York | Egyptian General Authority of Survey | -42 to -23 | 28.4 | +13 to +22 | 15.5 |
| London Europe/London | University of Islamic Sciences, Karachi | -21 to +0.0119 | 9.3 | 0 to +21 | 9.4 |
| London Europe/London | Muslim World League | -21 to +0.0119 | 9.3 | 0 to +14.0119 | 6.6 |
| London Europe/London | Moonsighting Committee Worldwide | -57.01428333333333 to +3 | 15.6 | -21.0119 to +17 | 10.3 |
| London Europe/London | Umm al-Qura, Makkah | -24 to +0.0119 | 10.6 | -15 to +27 | 10.3 |
| London Europe/London | Egyptian General Authority of Survey | -31 to +0.0119 | 12.7 | 0 to +17 | 8.0 |
| Sydney Australia/Sydney | University of Islamic Sciences, Karachi | -21 to -14 | 16.1 | +14 to +21 | 16.1 |
| Sydney Australia/Sydney | Muslim World League | -21 to -14 | 16.1 | +9 to +14 | 10.7 |
| Sydney Australia/Sydney | Moonsighting Committee Worldwide | -21 to -14 | 15.9 | -8 to +16 | 8.8 |
| Sydney Australia/Sydney | Umm al-Qura, Makkah | -24 to -16 | 18.8 | +6 to +22 | 16.5 |
| Sydney Australia/Sydney | Egyptian General Authority of Survey | -31 to -21 | 24.2 | +12 to +17 | 13.4 |
Why the differences cannot be explained by angles alone
The Fajr-angle comparison holds a simpler pair of presets side by side. Here we compare whole presets, including their seasonal rules, fixed intervals and built-in adjustments. In particular, Umm al-Qura uses a fixed Isha interval, while Moonsighting Committee applies seasonal rules.
For London, the same recommended high-latitude rule is supplied to each calculation, but the presets may handle twilight differently. A small difference on one summer date is not proof that two methods use the same dawn definition. See summer twilight and high-latitude prayer times.
Inputs and limitations
- One fixed GeoNames coordinate pair per city; no neighbourhood-specific or elevation correction.
- Adhan 4.4.6, with each city's recommended high-latitude rule and the presets implemented by SalahTable.
- No custom user offsets or official mosque schedules. The Umm al-Qura preset here retains its 90-minute Isha interval throughout the year; no extra Ramadan Isha adjustment is applied.
- Differences subtract UTC instants, including local date rollover. City clocks use IANA time zones; daylight saving is not treated as a calculation-method difference.
- Mean absolute values are rounded to one decimal minute. The result describes four cities and one year, not every location or future year.
Download and reproduce
The study calculates every date with the same engine as the site. The downloadable summary JSON also records the first date with the largest absolute difference for each row. Calculations are generated ahead of time so opening this article does not run a full-year study.
Our public 2027 release provides daily records for these cities and more. Its CSV delta columns use country defaults as their reference, whereas this article uses ISNA for every city. To reproduce this table from those records, subtract the ISNA timestamp from the compared method's timestamp for the same city and date.