Worst is when someone fucked up the DB time configs at some point and you have datetimes in a column that fall during the “nonexistent” hour in which clocks skip ahead for DST, and you have to figure out what the fuck actually happened there, and where in the data pipeline tz data was either added or stripped (sometimes it’s both, and sometimes it’s not just once), and undo the timestamp fuckery.

Source: did that this week. Was not super awesome.