A great many of the false assumptions listed were my own. Especially “time stamps are always in seconds since epoch” and “the duration of a system clock minute is always pretty close to the duration of a wall clock minute.” Whoa did I ever live to regret my ignorance in those two cases! But hey, apparently I’m not the only one who has run into (or inadvertently caused) such issues. A lot of people responded and shared similar experiences.
Good stuff - working with time is always lots of fun.