My favorite (kind of related) little gem from the postgresql documentation is from the century section of EXTRACT, date_part: https://www.postgresql.org/docs/9.5/static/functions-datetim...

Under the century section it notes:

"The first century starts at 0001-01-01 00:00:00 AD, although they did not know it at the time. This definition applies to all Gregorian calendar countries. There is no century number 0, you go from -1 century to 1 century. If you disagree with this, please write your complaint to: Pope, Cathedral Saint-Peter of Roma, Vatican."

I chuckle imagining someone in the Vatican mail room tossing aside one letter a year related to this.