To edit start, stop, elapsed, and paused date & time values:

Open a window that contains time records, and select an exiting time record or create a new time record.

Scroll horizontally until a start, stop, elapsed, or paused column is visible, and double-click the time record under the respective column.  Or select Edit Date & Time from the Time menu.

The Edit Date & Time sheet should now be visible.  Change any values such as the start time and elapsed time.

After all edits are made, the time values have be add up correctly.
The start date & time plus the elapsed time plus the paused time equals the stop date & time.  To correct any necessary values, click on one of the four buttons in the Adjust box.  For example, if you advanced the stop date & time by an hour, and you want the elapsed time adjusted to reflect this change, click on the Elapsed Time button and an hour will be added to the elapsed time.

Click OK when done, or Cancel to ignore any changes you made.