Weird thing.
During resize, the dragged end is always aligned with the background time cell. That is, you should never get 09:36:10 if you CellDuration is 30.
During move, the actual offset from the cell start is respected. E.g. and event starting at 09:10 will have NewStart of 10:10 when dragged to 10:00 cell (with CellDuration="30"). If you want to force the events to be aligned with cells you need to adjust the event start in the DB or after it has been moved.