Just spent over an hour on a call with another developer trying to work around Excel's weird way of managing dates - they're represented as a 64 bit floating point value representing the number of days since 1st January 1970 (yes, days - not seconds like sensible systems)

There is a library which does some of this but it comes unstuck with formatting, e.g. 01/06/2020 gets converted to 06/01/2020.

Also, I think we need to stop referring to the US as an 'advanced' country when they continue to use mm/dd date formats and imperial measurements.