Yes, Excel can be a pain with time formats.
I also ran into the 24 hour time entry problem. The MS recommended fix: make sure that the time format for the computer was 24 hour time. Yup... the whole system, it works and everyone on the PC has to work that way too.
Another Excel time quirk try adding worked hours that total more than 24. It wants to format it as whatever remainder of a 24h day. The MS "fix": a custom format [hh]:mm;@
After all this "time" and program versions, you would think they would get it right. The number of related complaints on these issues is astounding.
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