Hi Ralph
Backing up the file takes a copy of the last time the file was modified, but the filename is the current time.
So:
1. I have a file last saved at 3pm
2. At 4pm I make a change and hit 'Save'
3. TDL takes a backup of the file before saving (Last Mod: 3pm) and gives it the current time in its name (4pm)
4. TDL saves the tasklist which updates the modified time to 4pm