While you're at it, switch over to DD/MM/YYYY for the date format. The only 2 configurations that make sense is that or YYYY/MM/DD. Either go general to specific or specific to general, MM/DD/YYYY makes no sense.
For purposes of this post though, RFC 3339 and ISO8601 are identical. Dates in the format YYYY-MM-DD, so 2024-08-29 is both RFC3339 and ISO8601 compliant.
Here in the UK we would say "I will visit you on the 19th of September" for example. I have never heard anyone say the month first. It's just different custom. We also drive on the other side of the road..! At the beginning it would have been helpful if the world would have agreed on a standard either way. Then it would stop confusion. (And less car accidents from people on holiday/vacation on the wrong side of the road! 😅