South Korea: time zone history, and your birth hour
The clocks in South Korea have changed 28 times since 1900. Today they run on UTC+9; the last change was on 9 Oct 1988. 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 summer time from 1948: 60 minutes, enough to move about 50% of births into a different two-hour period.
Every era
| From – to | Clock | Versus today · births in another hour |
|---|---|---|
| 1 Jan 1900 – 1 Apr 1908 | UTC+8:28 local mean time | −32 min about 27% |
| 1 Apr 1908 – 1 Jan 1912 | UTC+8:30 standard time | −30 min about 25% |
| 1 Jan 1912 – 1 Jun 1948 | UTC+9 standard time | same |
1948–1954, 4 stretcheseach stretch
| UTC+10 in summer, UTC+9 the rest of the year | up to 60 min about 50% |
| 20 Mar 1954 – 5 May 1955 | UTC+8:30 standard time | −30 min about 25% |
1955–1961, 6 stretcheseach stretch
| UTC+9:30 in summer, UTC+8:30 the rest of the year | up to 30 min about 25% |
| 10 Aug 1961 – 10 May 1987 | UTC+9 standard time | same |
1987–1988, 2 stretcheseach stretch
| UTC+10 in summer, UTC+9 the rest of the year | up to 60 min about 50% |
| 9 Oct 1988 – today | UTC+9 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.
Born in summer time?
In each of these, the clocks ran ahead of standard time. A birth inside one happened that much earlier by the sun than the clock said; give the birthplace and this site’s calculator takes it off for you.
- From 10 May 1987, 02:00 to 11 Oct 1987, 03:00 · 60 minutes ahead
- From 8 May 1988, 02:00 to 9 Oct 1988, 03:00 · 60 minutes ahead
Times are on the local clock: when each began the clocks went forward, and when it ended they went back.