Is your feature request related to a problem? Please describe.
Currently (as far as I could tell) there is no way to back up messages within a specified time period, e.g. within the last year or from 2019-2020.

Describe the solution you'd like
Some option that allows the user to backup messages within a specific date range.

Additional context
I think this would pair well with #33, if you're considering both for implementation. I only really need to offload older messages so I can free up iCloud storage, so these two features in tandem would be fantastic for what I'm trying to do.