All of India uses one clock (IST), but the country is about 30° wide from east to west. The sky turns 15° every hour, so the moon reaches the eastern horizon of Kolkata or Guwahati long before it reaches Mumbai or Ahmedabad.
East to west: up to two hours
Between Arunachal Pradesh and Gujarat the difference in moonrise can be close to two hours. Between Kolkata and Mumbai it is usually 60–75 minutes.
North to south
Latitude also matters, because the Moon's path crosses the horizon at a slant. Depending on the season, a northern city can see the moon earlier or later than a southern city at the same longitude.
Why you may not see it at the exact minute
Moonrise is calculated for a flat, clear horizon. Buildings, trees, hills, haze and clouds can hide the moon for another 10–30 minutes. If you're waiting to break a fast, go to a rooftop or open ground and look towards the east (or the direction shown in our camera finder).