Why do train schedules change?

Train schedules change for several reasons including seasonal demand, track maintenance, gauge conversion projects, or the introduction of new trains. Indian Railways revises its timetable periodically usually twice a year through a process called the New Time Table when schedule changes for hundreds of trains are implemented. Temporary changes occur during monsoon season when train speeds are reduced in flood-prone areas. Construction work on tracks or stations may also require schedule adjustments. After a route is fully electrified or converted from metre gauge to broad gauge, the schedule may be revised to allow faster travel times.