Temporal Data Types
Clifford Simak wrote a science fiction novel entitled, Time Is the Simplest Thing, in 1977. He was wrong. And the problems did not start with the Y2K problems we had in 2000, either. The calendar is irregular and the only ISO Standard unit of time is the second; years, months, weeks, hours, minutes, and so forth are not part of the SI system, but are mentioned in the ISO standards as conventions.
SQL-92 added temporal data to the language, acknowledging what was already in most SQL products by that time. The problem is that each vendor made a trade-off internally. We will get into SQL code later, but it is better to start with foundations.
Leap years did not exist in the Roman or Egyptian solar ...