Time: UCT, local time, daylight - any standards? 
Author Message
 Time: UCT, local time, daylight - any standards?

I am working on a process controller which will be configered form
various host computers, but the controller is expected to operate
stand-alone for extended periods.
My controller uses time two different ways:
1)  it performs actions based on preset time schedules. These time
schedules are based on "LOCAL TIME".
2) it stores an activity log for subsequent reporting. Because these
controllers may be located all over the country, it would make sense
to keep the log's timestamp in Universal Coordinated Time (UCT)

I'm considering to specify the following:
1) all time is to be sent between the host and the controllers shall
be in UTC
To compute LOCALTIME, also specify the following:
2) the controller shall be configured to have a signed timezone offset
from the UCT time base in units of seconds.
3) the controllers shall be configured to perform daylight savings
calculation based on a specified algorithm:
  a) none - no daylight savings adjustment is to be performed
  b) standard North American - such as EST/EDT, and PST/PDT
  c) ??? what other algorithm should be included to support
"worldwide" installations?

I'm looking for a clean method to define the setting, maintenance, and
reporting time. Is there an accepted standard for this? I read through
the Microsoft C/C++ compiler Runtime Library Reference, but its
definition the ANSI C time functions (ctime(), localtime()) was not
conclusive, especially about the different daylight savings settings.

Please post replies to this group or e-mail to me at

Thanks in advance,

Frank Gasztonyi



Thu, 21 May 1998 03:00:00 GMT  
 Time: UCT, local time, daylight - any standards?

:
: Newsgroups: comp.lang.c.moderated

: X-Copyright: This article may not be distributed on a CD-ROM
:  or in printed form without prior written consent of the author.
:

:
: > 3) the controllers shall be configured to perform daylight savings
: > calculation based on a specified algorithm:
: >   c) ??? what other algorithm should be included to support
: > "worldwide" installations?
:
: Let the user configure date & time where an DST switch occurs. DST
: begins and ends on basically arbitrary dates. The fact that they have
: been picked until some time T following a specific algorithm does not
: guarantee that your government won't change that algorithm suddenly.
:
: E.g. most of western Europe will probably change it in some years.
Here, here.  There was much discussion around Easter in one of the
demon... usegroups about DST (demon is a large internet provider in the
UK, and it has its own usenet hierachy).  The conclusion as I recall
is that there is NO algorithm for determining UK summer time!
X-SMTP-Posting-Host: pires.demon.co.uk [Tue, 12 Dec 95 16:15:13 GMT]

***PLEASE*** make it entirely user configurable.
--
Martin Bonner
Pi Technology, Milton Hall, Cambridge, ENGLAND
+44 1223 441256



Sat, 30 May 1998 03:00:00 GMT  
 
 [ 2 post ] 

 Relevant Pages 

1. Time: UCT, local time, daylight - any standards?

2. Time: UCT, local time, daylight - any standards?

3. standard c library time.h and daylight savings time

4. How to convert local time to gmt using a local variable time zone per process/thread

5. How to convert local time with specific time zone to UTC time in Win32 API

6. Converting UTC time to local time

7. Convert local time to gmt time without using TimeZone Env variable

8. GMT time and Local time ?

9. How to convert GMT time to local time?

10. converting from Local Time to UTC time...

11. A question about time function and daylight saving.

12. Algorithm to calculate Daylight saving time.

 

 
Powered by phpBB® Forum Software