One related wrinkle that can catch out UK people (who tend to conflate local non-summer-time with UTC) is that the epoch is not midnight 1 Jan 1970 in UK time -

One related wrinkle that can catch out UK people (who tend to conflate local non-summer-time with UTC) is that the epoch is not midnight 1 Jan 1970 in UK time -- we were in the middle of a "UK time is GMT+1 all year round" experiment in 1970...