All-day events have strange date syntax in event details pop out

[edelstone]

The date of an all-day event has a weird syntax in the event details pop out.

For example, an all-day event set for December 10, 2022 shows a syntax of "Dec 10-9, 2022". Prior versions would have just said 'Dec 10, 2022".

[sfsam]

Ventura changed the way All-day events are handled so the code that displays them is off-by-one. I now detect macOS 13+ and handle All-day events differently.

Can you see if this works?
https://itsycal.s3.amazonaws.com/Itsycal-0.13.3-Bug213-000.zip

[edelstone]

@sfsam That fixes it.