What time of day do Apple TestFlight builds expire?

Question

Surprisingly, I can't seem to find an answer to this question:

What time of day do Apple TestFlight builds expire? Is it the upload timestamp plus 90 days? Or midnight of the 90th day? And if so, what time zone?

Answer 1

Of course, now that I posted the question I found the answer:

TestFlight build expiration is the upload timestamp plus 90 days.

This isn't given in App Store Connect build metadata, but it does appear in the TestFlight client app under the build's App Details.