Longhaul into UK, watch out, you could become Resident & liable for income tax!

[Time Traveller]

This quote

under the 183-day rule to count as a day any day upon which an individual is in the UK at the end of that day (i.e. at midnight)

comes directly from the HMRC's own guidance -

To me that is pretty clear that your example would equal three days (ie midnights) in the UK