I find it hard to believe that you can&#x27;t see how people are obviously using the word &quot;rescheduling&quot; in <i>relation to local wall-clock time</i>.  The wall-clock time as the reference point is how everyday people commonly use &quot;reschedule&quot;.  When we flip DST on and off, nobody says &quot;schools and banks got opening times got rescheduled.&quot;<p>And yet, you keep emphasizing &quot;rescheduling&quot; in relation to UTC instead of local time.  We <i>already know</i> that DST changes changes the underlying absolute time in UTC.  <i>And that&#x27;s the very reason why you cannot store a future datetime as UTC!</i><p>Here&#x27;s a trick question to put your advice about storing future appointments as UTC to the test:<p>You want to save a datetime for the New York Times Square midnight countdown to ring in the New Year on December 31, 2018 @ 11:59:45pm.  As far as the user is concerned, his&#x2F;her brain thinks in terms of <i>local wall clock time</i> and therefore, that would be 2018-12-31 23:59:45 ET. (Notice it is &quot;ET&quot; and not &quot;EST&quot; or &quot;EDT&quot;)<p>Do you think you can save that user-specified datetime to the database as UTC?<p>Do you think it&#x27;s 2019-01-01 04:59:45UTC ?  (Wrong answer.)<p>Do you think it&#x27;s 2019-01-01 03:59:45UTC ?  (Wrong answer.)<p>If you don&#x27;t see why <i>both</i> of those UTC choices are incorrect, please study the previous posts.<p>To recap the problems with UTC:<p>-- you don&#x27;t know in 2016 what future UTC timestamp to write to the database.  The user doesn&#x27;t know either.  Nobody knows.  It depends on what the government does in the next 3 years.<p>-- UTC implies scientific precision and writing it to the database for future datetimes will incorrectly advertise that you have the clairvoyance about future rules.  You don&#x27;t.<p>-- UTC is <i>correct abstraction level</i> for past events (server logs, audit logs) and future non-human generated scientific datetimes such as moon phases and solar eclipses.  UTC is the <i>incorrect abstraction level</i> for human generated appointments&#x27; datetimes.<p>Attempting to save a socially-constructed future &quot;wall-clock&quot; datetime as UTC is <i>throwing away information</i> the user gave you.  Stop advising people to do that.