[LEAPSECS] Future time

[Daniel R. Tobias]

On 19 Jan 2014 at 11:07, Gerard Ashton wrote:


> Date/time manipulation software sometimes converts a date expressed as day,

> month, year, time to a number, as in Excel. If the number counts leap

> seconds, and an event is more than 6 months in the future, it will be

> necessary to search for the number using a range rather than an exact

> number. 


Date/time software can be problematic in a number of ways in dealing 
with future appointments (and past events) that are anchored in local 
civil time. When it attempts to convert it to some internal numerical 
representation at entry time, this is often based on things in effect 
with respect to the time and place of entry, and wind up in the wrong 
time when, between the entry time and the event time, there's a shift 
such as daylight-saving or moving to a different time zone. It can be 
really tricky, for instance, to enter events to take place in a 
different city you're going to travel to, or in a season when the DST 
time shift is different from the present, without it getting 
"auto-adjusted" in an incorrect manner. Importing out-of-town 
convention schedules into an iPhone can be hit-and-miss depending on 
how time zones are coded in the file you're importing.

Not to mention what happens if, as has happened in lots of times and 
places, the government suddenly changes the time zone boundaries or 
DST rules, causing some future appointment to shift again.

When I'm making an advance dinner reservation for 7 PM on October 1, 
2014 in New York City, I expect that the time of this event will be 
fixed to the civil time in effect in that city on that date, possibly 
subject to arbitrary governmental fiat between now and then so that I 
can never be sure precisely what atomic-clock point that will refer 
to. Thus, I'd like any electronic storage of this appointment to be 
in terms of local civil time, so it makes the shifts correctly if its 
standard changes (including any intervening leap seconds, as well as 
other adjustments that might be much larger such as 1-hour shifts). 
Now, if the reservation happens to be at 2:30 AM on the night that 
daylight saving time springs forward, then I'm in trouble, which is 
why such shifts tend to be scheduled in the wee hours.

If, on the other hand, I want a precise interval in atomic seconds, 
such as to time an athletic competition or scientific experiment, 
then a stopwatch or countdown/count-up timer would be what I needed, 
with no necessary connection to civil time.

-- 
== Dan ==
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