[sllabres]

I don't want to be petty, but there is no 'winter time', only standard time and summer time or 'daylight saving time'.

I first heard the term 'winter time' when it was discussed to decide weather to keep DST permanently or if people would like to keep 'winter time' always. And of course who would want to have winter-something always. ;)

[keithwinstein]

If we're being really pedantic, in the U.S. context the zones observe "standard time" all year. "Standard time" refers to the standardization across the zone, and the practice of advancing the clock during daylight-saving time changes each zone's standard time. The Unix-style usage of "EST" vs. "EDT" isn't pedantically correct (e.g., New York observes "eastern standard time" even in summer).

See 15 U.S.C. §§ 260a & 263 (https://www.law.cornell.edu/uscode/text/15/chapter-6/subchap...).

[dragonwriter]

> and the practice of advancing the clock during daylight-saving time changes each zone's standard time.

Even more pedantically, “standard time” is not necessarily consistent across each zone (particularly, during the period for which in parts of the zone it is advanced by an hour) since "standard time” only advances for those states, or parts of states, for which an exemption is not in place.

So, the Unix-y convention of using PST for "Pacific Standard Time without advancement", and PDT for "Pacific Standard Time with advancement" is the simplest way of getting meaningful concise labels out of the US legal scheme. (This is only a theoretical issue for some US timezones, but it is a concrete one for at least the Pacific and Hawaii-Aleutian Time Zones.)