mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-11-01 07:33:12 +08:00
Chris Tate
d33b083a3b
Local setters and the field constructor convert a local time value to UTC by bracketing it with the zone offset a day before and after, then checking the candidate instants: three to five localtime(3) calls per conversion. In glibc each call takes the zone lock and, for dates past the zone file's last transition, parses the zone's rule string again. The offsets now come from a per-thread cache of offsets at UTC midnights: a day whose two midnights agree has that offset throughout, given at most one transition per day, which the conversion already assumes. A day with a transition still asks localtime for the instant. A change of process.env.TZ clears the cache.