[B2-devel] Patch for daylight savings time

[Brian J. <bjj...@us...>]

I finally tracked down why the MacOS time always reas as GMT when
running BII on Irix:  the __SVR4 case in TimerDateTime() wasn't
getting selected, since Irix defines _SVR4_SOURCE instead of __SVR4.

But even with fixed #ifdefs, it didn't pick up on daylight savings
time.  Apparently Irix uses separate globals for the offset from GMT
for daylight savings time and standard time.  The following seems to
do the right thing on Irix:

> cvs diff -u timer_unix.cpp
Index: timer_unix.cpp
===================================================================
RCS file: /cvs/BasiliskII/src/Unix/timer_unix.cpp,v
retrieving revision 1.9
diff -u -r1.9 timer_unix.cpp
--- timer_unix.cpp      2001/02/02 20:52:58     1.9
+++ timer_unix.cpp      2001/07/05 19:01:26
@@ -60,6 +60,9 @@
        time_t utc_now = time(NULL);
 #if defined(__linux__) || defined(__SVR4)
        time_t local_now = utc_now - timezone;
+#elif defined(sgi)
+       time_t local_now = utc_now - (localtime(&utc_now)->tm_isdst ?
+                                     altzone : timezone);
 #elif defined(__FreeBSD__) || defined(__NetBSD__)
        time_t local_now = utc_now + localtime(&utc_now)->tm_gmtoff;
 #else


I have no idea if "altzone" is supported on any other systems; the
Linux man pages don't mention it.

But wouldn't the easier way to do this be to call localtime(), and
reconstruct the local time in seconds from the tm_sec, tm_min,
tm_hour, tm_yday, and tm_year fields?  That way localtime() would do
all the timezone and daylight savings time adjustments, in a fully
portable way.

						Brian

--------------------------------------------------------------------

  "Think big thoughts but relish small pleasures."
                                        -- Life's Little Instruction Book