Time Zones
I was confused by the astrological chart generated for me by astro.com, which says that my birth place (Kuala Lumpur) was in the GMT+7:30 time zone. That totally defies my knowledge about time zones. For me, Malaysia and Singapore are in GMT+8:00. Period. We have no Daylight Saving Time, so no complications there.
First thing I did was to do a binary search on astro.com’s atlas query tool, and found that astro.com thinks that on May 1st, 1982, Kuala Lumpur transitioned from +7:30 to +8:00.
So, I did a bit of research and learnt something. I stumbled upon Helmer Aslaksen’s page, which contains very extensive explanation of the history of the time zone and its influences in our region. It turns out that astro.com was right – at the time of my birth, Malaysia was observing +7:30. Now I feel really stupid.
I then remembered that the entire timezones(tz) database is on any UNIX system with glibc installed. To view information about your location, look for the appropriate geographical location under /usr/share/zoneinfo and use ‘zdump -v’ to view the complete history of transitions in your location. For example, to see Singapore’s time zone history:
$ zdump -v Asia/Singapore Asia/Singapore Fri Dec 13 20:45:52 1901 UTC = Sat Dec 14 03:41:17 1901 SMT isdst=0 gmtoff=24925 Asia/Singapore Sat Dec 14 20:45:52 1901 UTC = Sun Dec 15 03:41:17 1901 SMT isdst=0 gmtoff=24925 Asia/Singapore Wed May 31 17:04:34 1905 UTC = Wed May 31 23:59:59 1905 SMT isdst=0 gmtoff=24925 Asia/Singapore Wed May 31 17:04:35 1905 UTC = Thu Jun 1 00:04:35 1905 MALT isdst=0 gmtoff=25200 Asia/Singapore Sat Dec 31 16:59:59 1932 UTC = Sat Dec 31 23:59:59 1932 MALT isdst=0 gmtoff=25200 Asia/Singapore Sat Dec 31 17:00:00 1932 UTC = Sun Jan 1 00:20:00 1933 MALST isdst=1 gmtoff=26400 Asia/Singapore Tue Dec 31 16:39:59 1935 UTC = Tue Dec 31 23:59:59 1935 MALST isdst=1 gmtoff=26400 Asia/Singapore Tue Dec 31 16:40:00 1935 UTC = Wed Jan 1 00:00:00 1936 MALT isdst=0 gmtoff=26400 Asia/Singapore Sun Aug 31 16:39:59 1941 UTC = Sun Aug 31 23:59:59 1941 MALT isdst=0 gmtoff=26400 Asia/Singapore Sun Aug 31 16:40:00 1941 UTC = Mon Sep 1 00:10:00 1941 MALT isdst=0 gmtoff=27000 Asia/Singapore Sun Feb 15 16:29:59 1942 UTC = Sun Feb 15 23:59:59 1942 MALT isdst=0 gmtoff=27000 Asia/Singapore Sun Feb 15 16:30:00 1942 UTC = Mon Feb 16 01:30:00 1942 JST isdst=0 gmtoff=32400 Asia/Singapore Tue Sep 11 14:59:59 1945 UTC = Tue Sep 11 23:59:59 1945 JST isdst=0 gmtoff=32400 Asia/Singapore Tue Sep 11 15:00:00 1945 UTC = Tue Sep 11 22:30:00 1945 MALT isdst=0 gmtoff=27000 Asia/Singapore Sun Aug 8 16:29:59 1965 UTC = Sun Aug 8 23:59:59 1965 MALT isdst=0 gmtoff=27000 Asia/Singapore Sun Aug 8 16:30:00 1965 UTC = Mon Aug 9 00:00:00 1965 SGT isdst=0 gmtoff=27000 Asia/Singapore Thu Dec 31 16:29:59 1981 UTC = Thu Dec 31 23:59:59 1981 SGT isdst=0 gmtoff=27000 Asia/Singapore Thu Dec 31 16:30:00 1981 UTC = Fri Jan 1 00:30:00 1982 SGT isdst=0 gmtoff=28800 Asia/Singapore Mon Jan 18 03:14:07 2038 UTC = Mon Jan 18 11:14:07 2038 SGT isdst=0 gmtoff=28800 Asia/Singapore Tue Jan 19 03:14:07 2038 UTC = Tue Jan 19 11:14:07 2038 SGT isdst=0 gmtoff=28800
Notice the cut-off at the end of 1981, when Singapore shifted to GMT+8:00. I can’t seem to find any information on who is right – the tz database or astro.com? Obviously, the tz database thinks that the transition from +7:30 to +8:00 was at Dec 31 16:30:00 1981 UTC.
Does your Windows box have this? (Use the time zone converter if you can’t get your hands on zdump, though you would have to perform a more superior algorithm than binary search to find out the transitions from this tool.)
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