Re: should GMime use GDateTime instead of time_t?

[Jeffrey Stedfast <jestedfa microsoft com>]

Yea, I’ve filed a bug report about this here:

https://bugzilla.gnome.org/show_bug.cgi?id=780594

I’ve also committed a patch to GMime already to use GDateTime after working around the issue (I was mistaken 
about “-0400” not working) by turning timezone names like “EDT” into a numeric offset, snprintf’ing that into 
a buffer and then passing that buffer to g_time_zone_new().

Jeff

On 3/27/17, 3:55 PM, "Albrecht Dreß" <albrecht dress arcor de> wrote:

    Hi Jeff:
    
    Am 27.03.17 15:28 schrieb(en) Jeffrey Stedfast via balsa-list:
    > When the timezone is "EDT" or "-0400", g_time_zone_new(const char *name) returns a GTimeZone just fine 
and I pass it off to g_date_time_new(), but if I then ask for the UTC offset from the GDateTime, I get back 0.
    > 
    > If I change the string to "EST" or "-0500", everything works perfectly and I get back exactly the UTC 
offset that I would expect (-5 hours).
    
    I guess the GLib functions (like tzset) use the iana zone info data base 
(<https://www.iana.org/time-zones>).  On my Ubuntu 16.04 system it is living in the folder 
/usr/share/zoneinfo.  But there is no "EDT" (or other daylight saving, like CEST) definition file.
    
    I wrote the tiny attached test app - passing "EDT" or "CEST" as 1st parameter fails as you described.  
Passing "EST" or "CET" or *any* numerical offset, including "-0400", returns the proper result.  If the time 
zone names are given, of course depending upon the input date:
    
    ---8<----------------------------------------------------------------------------------
    albrecht@deneb:~/Work$ ./gdatetimetest CET $(date +%s)
    ** Message: 1490643491 = 19:38:11 2017-03-27: interval 95: offset vs. UTC = 120 minutes
    albrecht@deneb:~/Work$ ./gdatetimetest CET 1490000000
    ** Message: 1490000000 = 08:53:20 2017-03-20: interval 94: offset vs. UTC = 60 minutes
    albrecht@deneb:~/Work$ ./gdatetimetest +0100 $(date +%s)
    ** Message: 1490643494 = 19:38:14 2017-03-27: interval 0: offset vs. UTC = 60 minutes
    ---8<----------------------------------------------------------------------------------
    
    Do you get a different result when using the pure libc functions (i.e. set TZ, use tzset(), and then 
localtime())?  At least running the "date" command from the console with TZ set to a dst time zone will 
/also/ return UTC:
    
    ---8<----------------------------------------------------------------------------------
    albrecht@deneb:~/Work$ TZ=CET date
    Mo 27. Mär 21:53:22 CEST 2017
    albrecht@deneb:~/Work$ TZ=CEST date
    Mo 27. Mär 19:53:24 CEST 2017
    albrecht@deneb:~/Work$ TZ=UTC date
    Mo 27. Mär 19:53:37 UTC 2017
    ---8<----------------------------------------------------------------------------------
    
    Hope this helps,
    Albrecht.