Convert To Irregular Time Intervals

I have a client that collects data from a manufacturing facility a one minute intervals. I already have sql statments to convert the 1 minute data to other timeframes (e.g. 30 min, 60 min, daily). However, now the client wants to look at data converted to irregular time intervals. For example, instead of looking at the first, second, third, etc. 60 minutes of a day, they wish to see data grouped irregularly: first 30 minutes, next 1 hr & 45 min, next 2 hours, next 1 hr & 30 min, etc. These irregular intervals could change; they may later want to look at the first hr, next 2 1/2 hrs, next 1/2 hour, etc.; or whatever strikes their fancy.

So far, all I've come up with is run one query for each desired time session and then do a join on all the resulting tables. Anybody have a better idea on how to do this?