On Mon, Jul 27, 2015 at 12:47 PM, Ethan Furman <ethan@stoneleaf.us> wrote:
To me, Paul's example is a datetime operation: you start with a datetime
(7am today), perform arithmetic on it by adding a period of time (one
day), and get a datetime as the result (7am tomorrow).

Well, OK, let's propose these wordings: It looks like a date
operation, ie, add one to the date, but in reality it's a time
operation, ie add 86400 seconds to the time. These things sound
similar but are very different.

I have to disagree.  If I have my alarm at 7am (localtime ;) so I can be at work at 8am I don't care exactly how many seconds have passed, that alarm better go off at 7am local time.

sure, but that is very much a Calendar operation -- "7am tomorrow", On the other hand, if you wanted to sleep a particular length of time,t hen you might want your alarm to go off "in 8 hours" -- that is a different operation.

Calendar operations are very, very useful, but not on the table in this discussion, are they?



Christopher Barker, Ph.D.

Emergency Response Division
NOAA/NOS/OR&R            (206) 526-6959   voice
7600 Sand Point Way NE   (206) 526-6329   fax
Seattle, WA  98115       (206) 526-6317   main reception