On 2025-02-20 02:45 PM, Paul Eggert via tz wrote:
On 2025-02-20 11:26, Tom Lane wrote:
I take the OP's point to be that if we're keeping it around for
System V compatibility, it ought to continue to mean what it meant
on System V
Unfortunately doing that would cause more trouble than it'd cure, as
the System V EST5EDT rules don't match what clocks do now in the
eastern US. I think they also don't correspond to what clocks did
there before 1970.
In other words, users don't really want true System V compatibility.
They just want to keep using the same name for US eastern time.
That's true for most users. But not necessarily for special cases.
For example, some professional video facilities might find it better to
ignore DST shifts to avoid discontinuities in the SMPTE video timecode,
which cannot tolerate a DST shift in some cases, essentially choosing to
run "permanent stand time". Yes, the display time would not match the
local wall clock in summer time, but that is less important than
continuous uninterrupted time. EST5EDT and the others (PST8PDT and
such) give administrators that option. I'm maintaining it in my work for
that reason.
