While the overall announcements of updated railway train timetable are typically announced during the Sep-Oct month of every year, railway train time table/station time table also change during the year. It is important to frequently keep checking rly time table for any changes during the entire year.
Trains can arrive at a station earlier than the scheduled arrival time as per Indian railway time table, but per strict rules they cannot depart earlier than the scheduled departure time as prescribed in Indian train time table.
Trains may or may not halt at a station as per the scheduled halt time as prescribed in the railway time table. In other words, trains can depart from a station before the scheduled halt time as per the railway timetable - provided they are not leaving the station before the scheduled departure time as per the railway time table.
In multiple stoppage sections of the train, train time table has substantial time buffer included as part of train schedule time table. This allows train to recover time if running in a delayed fashion.
For some trains, it is observed that IRCTC time table are different from what is prescribed in main Indian Railway Time Table. Travelers are suggested to double check.