On Tuesday, 31 December 2019, 16:36:02 GMT, Bruce Momjian <bruce@momjian.us> wrote:
Does the next decade start on 2020-01-01 or 2021-01-01? Postgres says
it start on the former date:
SELECT EXTRACT(DECADE FROM '2019-01-01'::date);
date_part
-----------
201
SELECT EXTRACT(DECADE FROM '2020-01-01'::date);
date_part
-----------
202
but the _century_ starts on 2001-01-01, not 2000-01-01:
SELECT EXTRACT(CENTURY FROM '2000-01-01'::date);
date_part
-----------
20
SELECT EXTRACT(CENTURY FROM '2001-01-01'::date);
date_part
-----------
21
That seems inconsistent to me. /pgtop/src/backend/utils/adt/timestamp.c
has this C comment:
* what is a decade wrt dates? let us assume that decade 199
* is 1990 thru 1999... decade 0 starts on year 1 BC, and -1
* is 11 BC thru 2 BC...
FYI, these two URLs suggest the inconsistency is OK:
https://www.timeanddate.com/calendar/decade.html https://en.wikipedia.org/wiki/Decade--
Bruce Momjian <
bruce@momjian.us>
http://momjian.us EnterpriseDB
http://enterprisedb.com+ As you are, so once was I. As I am, so you will be. +
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