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 <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + As you are, so once was I. As I am, so you will be. + + Ancient Roman grave inscription +