BaZi and Daylight Saving Time: Taiwan's 1946–1979 Table, and Where Else to Check
If you or the parents you are casting a chart for were born in Taiwan between the 1940s and the 1970s, check this table first. In a daylight-saving year, 9 o'clock on the birth certificate was 8 o'clock standard time. In our sample, about 43.0% of Taipei births on DST days change hour once corrected. Born somewhere else? The same logic applies wherever the clocks moved, and the regional notes below show where to look.
The days Taiwan's clocks ran an hour fast
| Year | Period | Why |
|---|---|---|
| 1937–1945 | Oct 1, 1937 to Sep 20, 1945 | Wartime Japan Standard Time (UTC+9), an hour ahead all year |
| 1946 | May 15 to Sep 30 | Daylight saving time |
| 1947 | Apr 15 to Oct 31 | Daylight saving time |
| 1948 | May 1 to Sep 30 | Daylight saving time |
| 1949 | May 1 to Sep 30 | Daylight saving time |
| 1950 | May 1 to Sep 30 | Daylight saving time |
| 1951 | May 1 to Sep 30 | Daylight saving time |
| 1952 | Mar 1 to Oct 31 | Daylight saving time |
| 1953 | Apr 1 to Oct 31 | Daylight saving time |
| 1954 | Apr 1 to Oct 31 | Daylight saving time |
| 1955 | Apr 1 to Sep 30 | Daylight saving time |
| 1956 | Apr 1 to Sep 30 | Daylight saving time |
| 1957 | Apr 1 to Sep 30 | Daylight saving time |
| 1958 | Apr 1 to Sep 30 | Daylight saving time |
| 1959 | Apr 1 to Sep 30 | Daylight saving time |
| 1960 | Jun 1 to Sep 30 | Daylight saving time |
| 1961 | Jun 1 to Sep 30 | Daylight saving time |
| 1974 | Apr 1 to Sep 30 | Daylight saving time |
| 1975 | Apr 1 to Sep 30 | Daylight saving time |
| 1979 | Jul 1 to Sep 30 | Daylight saving time |
Source: the IANA time zone database, Asia/Taipei (the same time zone data your browser and operating system use). Periods include both end days; the clocks changed around midnight.
How we counted: our engine drew random birth times (to the minute) within each period, 12,000 per group, and compared the four pillars cast straight from the clock hour with the exact, corrected pillars. The modern Taiwan group was born 1980–2010; the daylight-saving group, 1946–1979.
How to take it off
If the birth date falls inside one of the periods above, subtract one hour from the time on the certificate. Three situations need care:
- Born between midnight and 1 a.m.: subtracting an hour takes you back to 23:00 the previous day, the Late Zi hour of the day before. We change the day at 23:00, so the day pillar is still the certificate date and the hour is still Zi; schools that change the day at midnight would move the day pillar back one day.
- The day the clocks went forward: at midnight the clock jumped straight from 0:00 to 1:00, so that hour never appeared on any clock. A birth recorded in it was most likely written down in standard time, or recorded wrongly; check with family.
- The day the clocks went back: at midnight the clock returned to 23:00 of the previous day, so the 23:00 hour ran twice (when Japan time ended on September 21, 1945, it was the midnight hour that repeated). If you were born in that stretch, find out whether it was before or after the change; the tool on this page can calculate either.
Daylight saving time: a Si hour on the clock that was really Chen
Born June 10, 1975, 9:10 a.m., Taipei
- Daylight saving: from April 1 to September 30, 1975, Taiwan's clocks ran an hour fast. The birth certificate says 9:10; standard time was 08:10.
- True solar time: Taipei sits at 121.56°E, a degree and a half east of the zone's standard meridian, so add 6 minutes; the equation of time on June 10 is about +1 minutes. True solar time comes to 08:17.
- Result: entered as the Si hour straight from the clock, the hour pillar is Yi-Si (乙巳). Corrected, the birth falls in the Chen hour and the hour pillar is Jia-Chen (甲辰). The year, month and day pillars stay the same, but the whole hour pillar changes.
Born in Hong Kong, mainland China, Singapore or the West
| Region | When the clocks ran ahead of standard time | Notes |
|---|---|---|
| Hong Kong, Macau | Japan time in wartime, 1941–1945; almost every summer 1946–1976, plus 1979 | Dates changed every year, and some years switched at 3:30 a.m.; the tool follows the time zone data for each date |
| Mainland China | Summers 1986–1991 (mid-April or early May to mid-September) | There were earlier periods in the 1940s, but practice varied by region |
| Singapore, Malaysia | No daylight saving time | In 1982 both moved from UTC+7:30 to UTC+8, so the clock has run over an hour ahead of the sun since; that is a true solar time question |
| United States, Canada | Most summers; year-round "War Time" 1942–1945; and in the US, most of 1974 | Rules changed many times and differed between states and provinces; let the tool read the time zone data |
| United Kingdom, Europe | Most summers; the UK also kept summer time all year from 1968 to 1971 and had "double summer time" (two hours ahead) in the 1940s | Same advice: the time zone data handles the details |
| Australia, New Zealand | Most summers since the 1970s in New Zealand and several Australian states (not Queensland or Western Australia today) | Summer there runs roughly October to April |
A born-abroad chart always uses the local time and longitude of the birthplace. Do not convert it to Taiwan, Hong Kong or Beijing time.
One technical note for the year-round cases (US War Time, the US in 1974, Britain 1968–1971): our tool judges "standard time" by comparing January with July, so for those years it may report no daylight saving and show the extra hour as a larger longitude offset instead. The true solar time it arrives at is still right, because it is calculated from the clock offset actually recorded for that date.
Correct your birth time
Enter the Gregorian date, time and place from the birth certificate. The tool works through daylight saving time, the longitude offset, the equation of time, the Zi-hour day change and the solar term boundary in one go, then compares the result pillar by pillar with a chart cast straight from the clock hour. Everything is calculated in your browser; nothing is uploaded.
Enter the clock time exactly as the birth certificate shows it; the tool takes off daylight saving time itself, so do not subtract it first. The day changes at 11 p.m. If your birthplace is not listed, pick the city closest in longitude (one degree is only four minutes).
A straight word: correction only helps if the recorded time is accurate
Hospital records usually give the minute, but family memory is more often "a bit after nine in the morning." If the time could be ten or twenty minutes out, fine-tuning it is pointless. If your time is an estimate, rather than worrying about whether to correct it, cast both possible hours and see which chart sounds more like you. Everything on this site is for reference and entertainment.
Were the clocks moved on the day you were born?
Enter the date, time and place from your birth certificate. The tool checks for daylight saving time, takes it off, then works out true solar time and the exact four pillars.
Daylight saving time FAQ
Which years did Taiwan have daylight saving time?
1946, 1947, 1948, 1949, 1950, 1951, 1952, 1953, 1954, 1955, 1956, 1957, 1958, 1959, 1960, 1961, 1974, 1975, 1979. The dates varied; most years started in April or May and ended in late September or late October. From October 1937 to September 1945 Taiwan also used Japan time all year.
I was born during daylight saving time. How do I cast my BaZi?
Subtract one hour from the time on the certificate to get standard time, then cast the chart. If you were born between midnight and 1 a.m., the result falls at 23:00 the previous day, where the schools differ on when the day changes.
Do births under Japanese rule in Taiwan also need an hour taken off?
Yes. From October 1, 1937 to September 20, 1945, Taiwan used Japan Standard Time (UTC+9), an hour ahead of today's Taiwan time.
I was born in the US or UK. Do I need to correct for daylight saving?
Yes, if the clocks were on summer time that day. Rules changed many times, including year-round war time in the 1940s, so rather than working it out by hand, enter the date, time and city in the tool; it reads the historical time zone data for that date.