Use yyyy instead of YYYY
and it is better to only call formatDateTimeUTC once:
You are not the only one with this issue. Lots of applications will be running into this error, or have been running into it.
See this for a demo: https://mydemoversion8-sandbox.mxapps.io/p/ff/FormatDateTime
This is one of the most common date time errors that mendix developers make. For more details check: https://www.notion.so/gajduk/Common-date-time-mistakes-that-Mendix-developers-make-a5fd80fb1ca04affa44b6e6dc674ce20