Why sharing a time zone does not mean sharing prayer times
A civil time zone gives every city inside its borders the same wall-clock hour, so businesses, trains and broadcasts stay synchronised. Prayer times, however, track the sun's position relative to your local horizon and meridian.
Earth rotates 360° in 24 hours (1,440 minutes), which equals 1° of longitude every 4 minutes. Within any single time zone, the sun rises, reaches solar noon and sets earlier in eastern cities and later in western cities by almost exactly 4 minutes per degree of longitude.
Worked east–west comparisons on the March equinox (21 March 2027)
Near the March equinox, day length is nearly uniform across latitudes, isolating the pure longitude effect. Each pair below shares the exact same IANA time zone and country calculation method on SalahTable, yet their prayer starts differ by 29 to 62 minutes.
| Time zone / city pair | Longitude gap (×4 min/°) | Eastern city (Fajr / Dhuhr / Maghrib) | Western city (Fajr / Dhuhr / Maghrib) | West later by (Dhuhr / Maghrib) |
|---|---|---|---|---|
| Pakistan Standard Time (UTC+5) Lahore → Karachi | 7.3° (~29 min) | 4:45 AM / 12:11 PM / 6:14 PM | 5:20 AM / 12:40 PM / 6:43 PM | +29 min / +29 min |
| Indian Standard Time (UTC+5:30) Kolkata → Mumbai | 15.5° (~62 min) | 4:26 AM / 11:45 AM / 5:48 PM | 5:29 AM / 12:47 PM / 6:50 PM | +62 min / +62 min |
| US Eastern Time (UTC−4 on 21 Mar) Boston → Atlanta | 13.3° (~53 min) | 5:29 AM / 12:52 PM / 6:57 PM | 6:32 AM / 1:46 PM / 7:50 PM | +54 min / +53 min |
| Arabia Standard Time (UTC+3) Dammam → Makkah | 10.3° (~41 min) | 4:24 AM / 11:47 AM / 5:51 PM | 5:08 AM / 12:28 PM / 6:32 PM | +41 min / +41 min |
When latitude adds a second difference
At the equinoxes (late March and late September), the difference between two cities in the same time zone is almost entirely explained by (Δ longitude × 4 minutes)—for example, Lahore (74.3° E) and Karachi (67.0° E) are 7.3° apart, and both Dhuhr and Maghrib in Karachi fall 29 minutes after Lahore.
In June and December, latitude adds a second effect on Fajr, Sunrise, Maghrib and Isha (while leaving Dhuhr governed by longitude). Because Lahore (31.5° N) is further north than Karachi (24.9° N), Lahore has longer summer days and shorter winter days, so the Fajr and Maghrib gaps between Lahore and Karachi widen and narrow across the seasons while their Dhuhr gap stays near 29 minutes all year.
Practical takeaway for travellers and Ramadan
Never reuse a timetable from another city simply because both cities share PKT, IST, EST or AST. Always select your exact city on the SalahTable home page or country index (Pakistan, India, United States, Saudi Arabia).