Experimental Physics and
Industrial Control System

"Peregrine M. McGehee" <[email protected]> · Thu, 06 Dec 2001 14:54:47 -0700

Jim,

Jim Thomas wrote:
> 1)  Why 36?  If we're only doing nano-seconds, shouldn't it be 30?
> 

The extra six characters constitute the timezone designator - from my
orginal posting:
	TZD  = time zone designator (Z or +hh:mm or -hh:mm)

Although in practice we want UTC (EPICS_TS_MIN_WEST = 0) with
daylight savings time disabled - yet another issue!
Our patch is to follow Keck's example and explicitly set the 
dst offset to 0 for our timezone within tsStampToLocal() and 
tsStampFromLocal(). An environmental variable would be nicer, i.e.
EPICS_TS_USE_DST.

> 2)  The FITS standard (http://archive.stsci.edu/fits/fits_standard) does not
>     limit the time fields to seconds.  From the definition for the DATE
>     reserved keyword, "The decimal part of the seconds field is optional
>     and may be arbitrarily long, so long as it is consistent with the rules
>     for value formats (5.2)".  We happen to use hundredths of seconds.  The
>     above just indicates how the string form will appear.  IMHO we should
>     not have "ISOFITS" meaning seconds only.  I don't have a reasonable
>     solution for Maren's problem though :-(
> 

The options that come to mind include:
1) Add even more elements to tsDefs.h: enum tsTextType.
2) Break the tsStampToText API to add a precision arg. (UGLY!)
3) Add a timestamp precision environmental variable,
say EPICS_TS_SECS_PRECISION (suggested!).

Aloha,
	Peregrine
-- 
Peregrine M. McGehee	[email protected]	(505) 667-3273
Sloan Digital Sky Survey / Spallation Neutron Source
MS H820, Los Alamos National Laboratory, Los Alamos, NM 87545

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System