Support for updating the datetime for a scheduled task

[tejasjadhav]

It would be much convenient to change the scheduled date and time of an already scheduled task. This means, if a task is about to run at a specified date and time, then there should be some way to change this and schedule it at some other time. It can be preponed or postponed.

Also, changing the recurrence rule would affect all the subsequent runs and the updated recurrence rule would be in effect.