Here in the US we have the system of daylight savings time (DST), at least for now.
But did you know that the timezone you use includes that? Cause I sure didn’t.
EST/CST/MST/etc are for the standard time version of the time zone EDT/CDT/MDT/etc are for the DST adjusted periods!
Largely, I prefer to let libraries handle this for me, so I’ve never dug into the details. But this one is also interesting from the perspective of communications with others.