Western Indonesia: time zone history, and your birth hour
The clocks in Western Indonesia have changed 7 times since 1900. Today they run on UTC+7; the last change was on 31 Dec 1963. A calculator that uses today’s offset for every birth is out by some minutes for anyone born in any of the different eras below.
Since 1925, the widest gap is the wartime, on Tokyo time from 1942: 120 minutes, enough to move nearly all of births into a different two-hour period.
Every era
| From – to | Clock | Versus today · births in another hour |
|---|---|---|
| 1 Jan 1900 – 1 Jan 1924 | UTC+7:07 local mean time | +7 min about 6% |
| 1 Jan 1924 – 1 Nov 1932 | UTC+7:20 standard time | +20 min about 17% |
| 1 Nov 1932 – 23 Mar 1942 | UTC+7:30 standard time | +30 min about 25% |
| 23 Mar 1942 – 22 Sep 1945 | UTC+9 wartime, on Tokyo time | +120 min nearly all |
| 22 Sep 1945 – 1 May 1948 | UTC+7:30 standard time | +30 min about 25% |
| 1 May 1948 – 30 Apr 1950 | UTC+8 standard time | +60 min about 50% |
| 30 Apr 1950 – 31 Dec 1963 | UTC+7:30 standard time | +30 min about 25% |
| 31 Dec 1963 – today | UTC+7 standard time | same |
The second figure in each row is the births moved into another two-hour period: about m/120 of them when the clock is m minutes out. For Kuala Lumpur, 30 minutes out from 1946 to 1981, the measured share is 26.0% of 4,000 sampled births.