Re: Happens in Google sheets as well.
Unfortunately, the day doesn't really have "an end" point - there's a concrete *start* at 00:00, and various times leading up to that such as 23:59:59.9999. But no specific end point, just an analogue rollover. There's also no such time as 24:00; the constraint is 0 <= HH <= 23. So midnight is always YYYY-MM-DD 00:00, where DD represents the day that is just starting [which feels a bit counter-intuitive].
FWIW, the most serious Excel issue here doesn't seem to have been noted: the default association of a CSV with an application that doesn't handle CSV's properly. All one of those scientists has to do to destroy their data is double-click the file and then hit "Save"; there is no point at which it is even possible to intervene during the "import". This has caused grief in just about every business I've worked in, particularly when the marketing team have been involved.
Mine's the one with the group policy to associate CSV's with notepad....