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help / color / mirror / Atom feedFrom: Tom Lane <[email protected]>
To: H Witt <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: why at time zone tz_offset not equal tz_name? tz_name has same offset in pg_timezone_names
Date: Mon, 28 Apr 2025 23:07:35 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <OSBPR01MB29975FFDA1D860B20A8AC85C9B802@OSBPR01MB2997.jpnprd01.prod.outlook.com>
References: <OSBPR01MB299716C895A69A6DFCF3357C9B812@OSBPR01MB2997.jpnprd01.prod.outlook.com>
<OSBPR01MB29975FFDA1D860B20A8AC85C9B802@OSBPR01MB2997.jpnprd01.prod.outlook.com>
H Witt <[email protected]> writes:
> select
> '2025-02-03 15:04:05'::timestamptz at time zone '+08:00',
> '2025-02-03 15:04:05'::timestamptz at time zone 'Asia/Shanghai'
They're different because '+08:00' is read as a POSIX time zone
specification, which has the opposite sign convention to what
you are thinking. See
https://www.postgresql.org/docs/current/datatype-datetime.html#DATATYPE-TIMEZONES
and especially
https://www.postgresql.org/docs/current/datetime-posix-timezone-specs.html
and remember the adage "The great thing about standards is there are
so many to choose from". Sadly, with only two relevant standards
humanity has still managed to cover the design space of which
direction from Greenwich gets the positive sign.
regards, tom lane
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Subject: Re: why at time zone tz_offset not equal tz_name? tz_name has same offset in pg_timezone_names
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