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From: Steve Crawford <scrawford@pinpointresearch.com>
Date: Fri, 21 Nov 2025 16:09:01 -0800
Message-ID: <CAEfWYyzvM4XcfKunhvT1_xs_9rGnbXbRvnn_znQD4-Wg-aA5Vg@mail.gmail.com>
Subject: Unexpected date conversion results
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Either there is a bug in my understanding or one in PostgreSQL. I expect a
date value to follow the current time zone setting and be interpreted as
midnight at the start of the given date. In many cases it does. Shown below
are the postgresql.conf settings and the psql client settings showing the
time zone to be America/Los_Angeles:

postgresql.conf:
log_timezone = 'America/Los_Angeles'
timezone = 'America/Los_Angeles'

Client time zone setting:

steve=> show timezone;
      TimeZone
---------------------
 America/Los_Angeles


Here is the value returned by current_timestamp and current_date:

steve=> select current_timestamp;
       current_timestamp
-------------------------------
 2025-11-21 14:48:06.948845-08


steve=> select current_date;
 current_date
--------------
 2025-11-21


Casting the current_date to a timestamp with time zone returns the expected
value (midnight November 21 Pacific Standard Time)

steve=> select current_date::timestamptz;
      current_date
------------------------
 2025-11-21 00:00:00-08


The output of to_char shows the same expected value:

steve=> select to_char(current_date, 'YYYY-MM-DD HH24:MI:SSTZH');
        to_char
------------------------
 2025-11-21 00:00:00-08


However, extracting the epoch from current_date returns 4pm the prior day
(i.e. 2025-11-21 00:00:00-00), in other words midnight 2025-11-21 UTC which
seems to be inconsistent behavior:

steve=> select to_timestamp(extract(epoch from current_date));
      to_timestamp
------------------------
 2025-11-20 16:00:00-08


steve=> select to_timestamp(extract(epoch from current_date))::date;
 to_timestamp
--------------
 2025-11-20


steve=> select to_timestamp(extract(epoch from '2025-11-21'::date))::date;
 to_timestamp
--------------
 2025-11-20


There was a time, like version 9-dot-something, when the above queries
performed as expected returning midnight in the current time zone but I
haven't been able to find a change document indicating this as an expected
change.

-Steve

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<div dir=3D"ltr"><div dir=3D"ltr"><div>Either there is a bug in my understa=
nding or one in PostgreSQL. I expect a date value to follow the current tim=
e zone setting and be interpreted as midnight at the start of the given dat=
e. In many cases it does. Shown below are the postgresql.conf settings and =
the psql client settings showing the time zone to be America/Los_Angeles:</=
div><div><br></div><div>postgresql.conf:</div>log_timezone =3D &#39;America=
/Los_Angeles&#39;<br>timezone =3D &#39;America/Los_Angeles&#39;<br><br>Clie=
nt time zone setting:<br><br></div><blockquote style=3D"margin:0 0 0 40px;b=
order:none;padding:0px"><div>steve=3D&gt; show timezone;</div><div>=C2=A0 =
=C2=A0 =C2=A0 TimeZone =C2=A0 =C2=A0 =C2=A0 </div><div>--------------------=
-</div><div>=C2=A0America/Los_Angeles</div></blockquote><div dir=3D"ltr"><b=
r>Here is the value returned by current_timestamp and current_date:<br><br>=
</div><blockquote style=3D"margin:0 0 0 40px;border:none;padding:0px"><div>=
steve=3D&gt; select current_timestamp;</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=
=A0current_timestamp =C2=A0 =C2=A0 =C2=A0 </div><div>----------------------=
---------</div><div>=C2=A02025-11-21 14:48:06.948845-08</div></blockquote><=
div><br></div><blockquote style=3D"margin:0 0 0 40px;border:none;padding:0p=
x"><div>steve=3D&gt; select current_date;</div><div>=C2=A0current_date </di=
v><div>--------------</div><div>=C2=A02025-11-21</div></blockquote><div><br=
>Casting the current_date to a timestamp with time zone returns the expecte=
d value (midnight November 21 Pacific Standard Time)<br><br></div><blockquo=
te style=3D"margin:0 0 0 40px;border:none;padding:0px"><div>steve=3D&gt; se=
lect current_date::timestamptz;</div><div>=C2=A0 =C2=A0 =C2=A0 current_date=
 =C2=A0 =C2=A0 =C2=A0</div><div>------------------------</div><div>=C2=A020=
25-11-21 00:00:00-08</div></blockquote><div><br>The output of to_char shows=
 the same expected value:<br><br></div><blockquote style=3D"margin:0 0 0 40=
px;border:none;padding:0px"><div>steve=3D&gt; select to_char(current_date, =
&#39;YYYY-MM-DD HH24:MI:SSTZH&#39;);</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =
to_char =C2=A0 =C2=A0 =C2=A0 =C2=A0 </div><div>------------------------</di=
v><div>=C2=A02025-11-21 00:00:00-08</div></blockquote><div><br>However, ext=
racting the epoch from current_date returns 4pm the prior day (i.e. 2025-11=
-21 00:00:00-00), in other words midnight 2025-11-21 UTC which seems to be =
inconsistent behavior:<br><br></div><blockquote style=3D"margin:0 0 0 40px;=
border:none;padding:0px"><div>steve=3D&gt; select to_timestamp(extract(epoc=
h from current_date));</div><div>=C2=A0 =C2=A0 =C2=A0 to_timestamp =C2=A0 =
=C2=A0 =C2=A0</div><div>------------------------</div><div>=C2=A02025-11-20=
 16:00:00-08</div></blockquote><div><br></div><blockquote style=3D"margin:0=
 0 0 40px;border:none;padding:0px"><div>steve=3D&gt; select to_timestamp(ex=
tract(epoch from current_date))::date;</div><div>=C2=A0to_timestamp </div><=
div>--------------</div><div>=C2=A02025-11-20</div></blockquote><div><br></=
div><blockquote style=3D"margin:0 0 0 40px;border:none;padding:0px"><div>st=
eve=3D&gt; select to_timestamp(extract(epoch from &#39;2025-11-21&#39;::dat=
e))::date;</div><div>=C2=A0to_timestamp </div><div>--------------</div><div=
>=C2=A02025-11-20</div></blockquote><div><br></div><div>There was a time, l=
ike version 9-dot-something, when the above queries performed as expected r=
eturning midnight in the current time zone but I haven&#39;t been able to f=
ind a change document indicating this as an expected change.</div><div><br>=
</div><div>-Steve</div>
</div>

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