[whswhs]

It looks like the multiplier for a step is approximately 5; that is, "a number that is closer to 5 than to 0 or 10." So for shorter intervals, I would say 6 hours, 1 hour, 15 minutes, 5 minutes, 1 minute, 15 seconds, 5 seconds, 1 second. For longer ones, probably 6 months, 2 years, 10 years, 50 years, 200 years, 1000 years. Those are mostly between 4 and 6, but are also conveniently round time periods.