Your app still needs to know what is coming in, and convert that to its internal format.
Even if you want to get everyone to agree on XML Schema's datetime format, it's not always sufficient because sometimes you need the actual time zone (e.g. America/New_York ) rather than the UTC offset especially when dealing with recurring/far off events.
ISO 8601, as used by XML Schema:
<foo>2020-09-04T00:00:00Z</foo>
or
Unix date output format (not sure this has an actual name)
<foo>Fri 04 Sep 2020 00:00:00 GMT</foo>
or
some sort of destructured date
<foo> <year>2020</year> <month>09</month> <day>04</day> <!-- ... --> </foo>
or
some sort of destructured date with 0 based months because Java
<foo> <year>2020</year> <month>08</month> <day>04</day> <!-- ... --> </foo>
Your app still needs to know what is coming in, and convert that to its internal format.
Even if you want to get everyone to agree on XML Schema's datetime format, it's not always sufficient because sometimes you need the actual time zone (e.g. America/New_York ) rather than the UTC offset especially when dealing with recurring/far off events.