keep-all-since datetime not yet implemented

[airforceboricua]

Are there any plans to implement this option? Could really use this tag if at all possible.

Thank you!

[ehammond]

@airforceboricua I haven't written it yet, but if you would be willing to test this, drop me an email (first name @ alestic.com).

I'm also happy to review pull requests if somebody else would like to tackle it. My vision was for the human time string to be parsed with Date::Manip, which gives lots of flexibility.