Add older data to repo

I dump and backup some LXCs 3 times a week using restic. Works like a charm. Before, I used something else.

Idea: restore data from old backup program and back it up with restic. I’d profit from dedup and could dump the old program.

Question: How would I know which snapshot contains the old data? Can I change a snapshots’ date? Any other ideas?

Sure, restic backup has a flag for it:

--time time     time of the backup (ex. '2012-11-01 22:08:41') (default: now)