ISO Standard for date/time

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: ISO Standard for date/time
• From: "Unidata User Support" <support@xxxxxxxxxxxxxxxx>
• Date: Thu, 25 Mar 93 09:31:41 -0700

From: 24-Mar-1993 2109 <lysakowski@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 24 Mar 93 18:26:59 -0800
Cc: lysakowski@xxxxxxxxxxxxxxxxxxx
Subject: ISO Standard for date/time 
Organization: . 
Keywords: 199303250227.AA19629 

Why don't you just use the ISO standard for date/time stamps?  

These are:

ISO Standard 2014-1976 (E) "Writing of Calendar Dates in All-Numeric Form".

ISO Standard 3307-1975 (E) "Information Interchange - Representations of 
Time of the Day".

ISO Standard 4031-1978 (E) Information Interchange - Representations of 
Local Time Differentials".

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What these translate into are:

YYYYMMDDhhmmss.+/-ffff

For example "19910801123023-0500" is 12:30 P.M. on August 1, 1991 in New 
York City.   Note that -0500 is 5 full hours behind Greenwich Mean Time.

The ISO standards permit the use of separators, if they are required to 
facilitate human understanding.   

For example:  1991,08,01,12:30:23-0500.

ISO may have revised it recently to take fractions of seconds into 
account.  What they've done for UDUNITS looks pretty close to ISO, but it 
doesn't comply with the international standard.  For something as universal 
as date/time stamp this compliance is pretty important.  Anyone know why 
the ISO standard wasn't used?

Rich 
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>From: blincoln@xxxxxxxxxx (Brian Lincoln)
Date: Wed, 24 Mar 93 15:14:05 -0600
Subject: Re: A standard for time and labelling problems 

> >From: rakesh@xxxxxxxxxxxxxxxxxxxxxxxx
> >Date: Wed, 24 Mar 93 09:49:12 -0500
> >Subject: Re: A standard for time and labelling problems 
> 
> We have used the Unix standard of time, i.e. seconds since Jan. 1, 1970.
> This way we can store time as one long integer (4 bytes) per time value,
> and are able to store time values in sec from year 1902 through year 2038.
> Unix utilities can then be used to convert time into any form you want, e.g.
>       Date format: yyyy/mm/dd/hh:mm:ss
>       Julian date format: yy/dd/hh:mm:ss
>       String format: Ex: Fri May 15 16:12:19 1992

have you seen the UDUNITS stuff from ucar? its available at unidata.ucar.edu
and it has a format similar to, but not the same as you have above..
the order is a little more regular in the string and is
" units since int year int month int day int hour int min double sec int ucthr
  int utcmin"
so " Seconds since 1992-5-15 16:12:19.0 -5:00"

for your example above...
and then a variable "time" is defined as a double offset.. im sure it
wouldnt be too much of a stretch to use another vardef .. NC_LONG or something
(if you think that 8 bytes is too many for a timestamp)
but the UDUNITS standard is double..

.. hope this isnt just noise...

bcl
blincoln@xxxxxxxxxx

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