Hey Chad,
I don't have a regex for you, but if you have access to the implementation itself as an alternative the most recent timeparting plugin provides an array of info including the time to the minute, time to the current 30min block, day of week and weekday/weekend.
I then concatenate all of these values into a single eVar for collection and use auto classification rules to separate out each component into a minute/30min/day classification of that eVar.
Hope that helps - if you don't have the timeparting code ClientCare should be able to help with the plugin & documentation, if you use appMeasurement make sure you also have the compatibility plugin.
Cheers, Jez