Timestamp helpers output an incorrect number of days for timestamps above 30 days

The humanTimedelta and preciseHumanTimedelta helpers convert an amount of seconds to a readable string. The "precise" version, used for worker activities, shows a combination of multiple units, like 2 days 3 hours 4 minutes 5 seconds 6 milliseconds. The non-precise version picks the most appropriate unit, like 1 day when the duration exceeds 24 hours. The largest defined unit is days, so a duration above 30 days should just keep displaying 83 days. The 30 day limit should only matter for another helper function, ago, where any date above 30 days is displayed as an absolute RFC 3339 date instead of a readable duration.

I noticed that some old processes that finished without having a finished date set have strange durations: a process that's 83 days old was displaying Running for 2 days instead of Running for 83 days. Turns out it is displaying the number of "months", assuming a month is always exactly 30 days (I love calendars). The "precise" helper instead displays 23 days 22 hours ..., aka 83 % 30 days.