Using more human readable date/time formats

I updated the regexes to allow for backwards compatibility as well.  All new archives will follow the YYYY-MM-DD_HH:MM_UTC format, but older archives following the YYYYMMDDHHMMUTC format will also work.  I haven't figured out a way to skip parsing older archives automatically if they don't exist.  I suppose I could default to checking them first and then try / except on the original format.  What do you think?