st: Re: time manip

[Christopher F Baum <baum@bc.edu>]

--On Saturday, September 28, 2002 2:33 -0400 Jesper wrote:

> I agree that it might be nice in some situations to have a format that
> specified the exact time as well as the day.
>
>
>  So, unless you truncate it, the granularity of the timing is in the
> daystamp variable.
As proposed, an approximation of the timing to the second is in the 
daystamp variable. Since the number of seconds since the epoch is a 9 digit 
number, the proposed calculations should be generated as doubles; otherwise 
applying this transformation and its inverse will not yield the original 
timestamp. A second off here, a second off there, and averages or other 
summary stats based on these calculations will be imprecise.

It would be very useful to have a set of functions that allow you to work 
directly with the *nix time, which allows for exact arithmetic since it is 
an integer. I should not have to transform data into fractional days and 
then back again to do differencing arithmetic (how long, in minutes, 
between successive doses of the drug?) Those calculations using epoch time 
are trivial. Then all that is needed is the ability to take a number of 
seconds and format it as elapsed HH:MM[:SS], as Jesper suggests.

Kit
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