Support different duration values

[ces3001]

I have years of duration data in human-friendly format of, for example, "5h 30m" (for 5 hours and 30 minutes), and “15m” for 15 minutes.

Is it possible to implement a duration interpreter that can parse Hours (%H) and Minutes (%M) and Seconds (%S) if desired from arbitrary strings? (use strptime?) Or if not arbitrary strings, then the common possibilities: “%Hm %Mm” “%H hours %M mins” “%H:%M:%S” “%Mm” “%Mmins” etc.

The only currently acceptable "%H:%M:%S" format is ugly for me because it looks like a time, not a duration.