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Born During Daylight Saving Time? Your BaZi Hour May Be Off

By Data Saju · Published October 12, 2026

BaZi sets your hour pillar by the Sun, not the clock, so if daylight saving time (DST) was in effect when you were born, the extra hour has to come off. For births during DST, half of all clock times land in a different two-hour Earthly Branch once it is removed, and across a whole year of U.S. births since 2007, 31.4% of hour pillars differ from a clock-only reading. Our almanac engine counted it for New York in nine sample years, and for Korea's own daylight saving years.

Does BaZi use daylight saving time?

BaZi uses local solar time: the hour pillar is the two-hour period (an Earthly Branch such as Horse 午 or Goat 未) that the Sun's position puts you in, not the number on the wall clock. Daylight saving time moves the wall clock one hour ahead of standard time, so a birth at 1:30 PM on a July afternoon happened at 12:30 PM by standard time. Because each hour pillar is two hours long, an hour shift moves half of all birth times into the neighboring pillar.

Here is a worked example with the engine (a made-up birth, not a real person): July 17, 2024, 1:30 PM in New York.

The day pillar stays 壬午 in all three, but the hour pillar moves from the Goat hour to the Horse hour, and the hour stem changes too (丁未 vs 丙午). Longitude matters as well: New York is at 74.01° W, so local solar time is 4 minutes ahead of the clock in winter and 56 minutes behind it in summer (the DST hour minus those 4 minutes).

How many people does this affect? A year-by-year count

U.S. daylight saving rules changed many times, so how many births fall in DST depends on the year. For each year below we took every fifth day of the year, ran New York times through the engine at 7-minute steps, and compared the hour pillar with a calculator that reads the clock as standard time (ignoring DST). Birth times are assumed to be evenly spread across the day.

• Before 1967, U.S. daylight saving time was set by local option, so it depended on the city (New York City used it from late April to October).
• The Uniform Time Act of 1966 set one national schedule from 1967; in 1974 and 1975 an energy-saving law started DST in January and February, which makes those two years the most affected in our table (38.7% and 32.6%).
• A 1986 law moved the start to the first Sunday in April from 1987, and the Energy Policy Act of 2005 moved it to the second Sunday in March and the end to the first Sunday in November from 2007. The extra weeks in spring and fall are why 2007 onward (238 days) is higher than 2006 (210 days).
• Hawaii and most of Arizona do not observe DST: the engine counts 0 DST days in 2024 for both Honolulu and Phoenix, so a clock reading is already standard time there.

Sources: the IANA time zone database (rules and comments on the 1966, 1974–75, 1986 and 2005 laws), U.S. Naval Observatory and timeanddate.com on the Energy Policy Act of 2005. DST day counts and percentages were calculated by this site's engine.

What clock time does each BaZi hour start? (New York)

These are the clock times, read off the engine minute by minute, at which each two-hour BaZi period starts and ends for a New York birth.

So in winter the Horse hour runs from 10:57 AM to 12:57 PM on the clock, and in summer from 11:57 AM to 1:57 PM. This applies to New York only, because the shift depends on longitude; use the checker below for your own city.

Check your own birth time

Enter the time exactly as it appears on the birth certificate, without subtracting the DST hour yourself. Everything is calculated in your browser and nothing is sent anywhere.

Korea ran daylight saving too: the 1987–88 case

If you were born in Korea, the same issue applies, with its own dates. South Korea used daylight saving time in 1948–51, 1955–60 and 1987–88, and its standard time was UTC+8:30 from March 21, 1954 until August 9, 1961 (IANA time zone database). In 1987 and 1988 DST ran 155 days each year, so the hour pillar changes for 20.7% of 1987 births and 21.3% of 1988 births compared with a reading that treats the clock as always UTC+9. Our Korean article, 1987·88년생은 사주가 바뀔 수 있다, has the full table.

Frequently asked questions

Do I subtract the daylight saving hour from my birth time for BaZi? Yes, the hour pillar is based on solar time, so the extra DST hour comes off. Our reading does it for you from your birth date and birthplace; just enter the time on your birth certificate.

How often is the hour pillar wrong if DST is ignored? For births while DST was in effect, half of all clock times fall in a different hour pillar. Over a whole year it is 31.4% in New York since 2007, and 38.7% in 1974 when DST began in January.

Does daylight saving time change my day pillar? Rarely: only about 2.8% of birth times in a year, those in the hour around midnight.

Do Hawaii and Arizona need a correction? No DST correction: neither observes DST (the engine finds 0 DST days in 2024), though the small longitude shift still applies.

What if I was born in the hour that was skipped in spring? That clock time did not exist, because clocks jumped from 2:00 to 3:00 AM. Check the certificate; the checker above uses the nearest valid time.

Counts come from this site's almanac engine: every fifth day of each listed year, at 7-minute steps in New York time, with birth times assumed evenly spread through the day. Rules and dates come from the sources linked above.

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