[LEAPSECS] Future time

[Brooks Harris]

On 2014-01-19 08:07 AM, 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. For example, if Excel were revised to account for leap seconds, and

> one wanted to search for 8 PM January 14, 2015, rather than searching for

> 42018.8333... one would have to search for something like a time t, where

> 42018.83332 < t < 42018.83335. This of course overlooks whatever "fuzz"

> Excel may silently employ in searches.

Use extreme caution with Excel - for examples -

http://support.microsoft.com/kb/214094

http://www.mathworks.com/help/matlab/import_export/when-to-convert-dates-from-excel-files.html

http://answers.oreilly.com/topic/1700-how-to-calculate-the-difference-between-dates-in-excel-using-datedif/

Also be very careful with calculations - its floating point.


>

> Gerard Ashton

>

> -----Original Message-----

> From: leapsecs-bounces at leapsecond.com

> [mailto:leapsecs-bounces at leapsecond.com] On Behalf Of Daniel R. Tobias

> Sent: Sunday, January 19, 2014 10:35 AM

> To: Leap Second Discussion List

> Subject: Re: [LEAPSECS] Future time

>

> On 18 Jan 2014 at 19:51, Warner Losh wrote:

>

>> Of course, the 6 month window does make it impossible to compute a

>> time_t for a known interval into the future that's longer than 6 months

> away...

>

> What are the applications that actually need to schedule events more than 6

> months in the future that need to be precisely synchronized to civil time at

> a resolution of under a second? Gee, I might miss the plane for the airline

> reservation I made 7 months in advance if I show up one second late!

> (Actually, both myself and the airline, if we care about this level of

> detail, will have adjusted our clocks/watches by flight day, including any

> leap seconds in the interim, and I'll be right on time.)

>

> --

> == Dan ==

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>

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