An older, and IMHO slightly more authoritative, source: <https://wiki.c2.com/?TestIfDateRangesOverlap>
See also: <https://martinfowler.com/eaaDev/Range.html>
See also: <https://martinfowler.com/eaaDev/Range.html>
Hey, _I'm_ a source that's older than that one: <https://stackoverflow.com/a/13513973>
Not so sure about "more authoritative", though.
The earliest version I could find on IA is from 2003 (https://web.archive.org/web/20030606033520/http://c2.com/cgi...), last edited in 2002 at that point, but wouldn't surprise me to page was initially created in the 90s.