LONGITUDE is equal to 4 minutes.15 degree longitude is 1 hour.When one crosses International DATE Line, day and date changes.When one crosses IDL to west, one loses the day.When one goes from west to east, one GAINS a day.Russia has highest number of time zones.Prime meridian passes through Greenwich in ENGLAND which is zero degree longitude.Opposite of prime meridian is IDL which is at 180 degree longitude.IDL is a zigzag line and passes through Bering Strait.