True solar time · By city
True Solar Time in New York
Auspice ·
纽约 · 真太阳时
In New York, true solar time runs anywhere from 66 minutes behind the clock to 20 minutes ahead of it. Across every clock minute of 1980, 1990, 2000, 2010, 29.4% land in a different BaZi hour pillar once corrected (45.5% under daylight saving, 7.7% outside it), and 2.5% on a different day pillar.
How often does the hour pillar change in New York?
| Clock minutes whose hour pillar changes | 29.4% |
| Range across 1980, 1990, 2000, 2010 | 26.2% – 32.5% |
| During daylight saving | 45.5% |
| Outside daylight saving | 7.7% |
| Share of minutes under daylight saving | 57.5% |
| Clock minutes whose day pillar changes | 2.5% |
| Correction range | −66 … +20 min |
From the 40-city study on the main true-solar-time page: every clock minute of 1980, 1990, 2000, 2010 in the America/New_York time zone at 74°W, converted to true solar time. Minutes are weighted equally, so this is a per-minute figure, not a per-birth one. Data: /data/solar-time-study.json (CC BY 4.0).
Why the clock and the sun disagree here
New York is at 74°W; its standard clock follows the 75°W meridian (UTC−5). The earth turns one degree every four minutes, so the longitude part of the correction is +4 minutes, the same every day of the year. The equation of time adds a seasonal swing of roughly −15 to +16 minutes. Daylight saving adds another −60 minutes whenever it is in force, which was 57.5% of clock minutes across the study years. That is why the rate under daylight saving (45.5%) is so much higher than outside it (7.7%).
New York's clock since 1940
A chart has to use the clock that was in force on the birth date, not today’s. The table below is read directly from the IANA time-zone database the calculator uses, so it lists exactly the offsets a chart for each period is computed with.
| From | Until | Clock | Longitude part | Note |
|---|---|---|---|---|
| already in use in 1940 | 9 February 1942 | UTC−5 | +4 min | plus −60 min in daylight-saving months |
| 9 February 1942 | 30 September 1945 | UTC−4 | −56 min | clocks one hour ahead all year |
| 30 September 1945 | today | UTC−5 | +4 min | plus −60 min in daylight-saving months |
Dates are the local day the clock changed. The longitude part is what the correction would be from longitude alone on that clock.
Daylight-saving rules by year
| Years | Starts | Ends | Clock in summer |
|---|---|---|---|
| 1940–1941 | last Sunday of April | last Sunday of September | UTC−4 |
| 1946–1954 | last Sunday of April | last Sunday of September | UTC−4 |
| 1955–1973 | last Sunday of April | last Sunday of October | UTC−4 |
| 1974 | first Sunday of January | last Sunday of October | UTC−4 |
| 1975 | last Sunday of February | last Sunday of October | UTC−4 |
| 1976–1986 | last Sunday of April | last Sunday of October | UTC−4 |
| 1987–2006 | first Sunday of April | last Sunday of October | UTC−4 |
| 2007–2026 | second Sunday of March | first Sunday of November | UTC−4 |
A birth in the week around a change date is worth checking by hand: the same clock reading can fall on either side of it depending on the year.
Worked examples for New York
Each birth is cast twice by the same engine as the calculator: once on the clock time as written, once corrected to true solar time. Same-day convention for the late Rat hour.
10 February 1974, 05:30
A February dawn in 1974, during the energy-crisis winter when daylight saving started in January.
| By the clock | By the sun | |
|---|---|---|
| Time | 05:30 | 04:19 |
| Hour pillar | 癸卯 (Rabbit hour) | 壬寅 (Tiger hour) |
| Day pillar | 壬午 | 壬午 |
Correction −71 min: daylight saving −60, longitude +4, equation of time −15. The hour pillar changes from 癸卯 (Rabbit hour) to 壬寅 (Tiger hour).
1 August 1985, 21:15
A summer evening under Eastern Daylight Time.
| By the clock | By the sun | |
|---|---|---|
| Time | 21:15 | 20:13 |
| Hour pillar | 辛亥 (Pig hour) | 庚戌 (Dog hour) |
| Day pillar | 壬申 | 壬申 |
Correction −62 min: daylight saving −60, longitude +4, equation of time −6. The hour pillar changes from 辛亥 (Pig hour) to 庚戌 (Dog hour).
3 November 1985, 21:15
The same clock time in early November, back on standard time, when the equation of time is near its yearly peak.
| By the clock | By the sun | |
|---|---|---|
| Time | 21:15 | 21:35 |
| Hour pillar | 己亥 (Pig hour) | 己亥 (Pig hour) |
| Day pillar | 丙午 | 丙午 |
Correction +20 min: daylight saving 0, longitude +4, equation of time +16. The hour pillar stays 己亥 (Pig hour).
About the clock in New York
New York City is at about 74.0°W, one degree east of the 75.0°W meridian. On standard time the sun is slightly ahead of the clock, peaking around 11:56. That is why, outside daylight saving, a New York birth rarely changes hour pillar; almost all of the change comes in the daylight-saving months.
The dates have moved several times within living memory. Year-round war time ran from February 1942 to September 1945. During the oil crisis Congress started daylight saving on 6 January 1974 and on 23 February 1975, then returned to the April start. The Energy Policy Act of 2005 moved the start to the second Sunday in March and the end to the first Sunday in November from 2007. A March or late-October birth from before 2007 therefore sits on a different clock from one born on the same date after.
To apply all of this to one birth, enter the date, clock time and New York as the birthplace in the free BaZi calculator. It uses the same historical clock and the same three-part correction, shows the arithmetic, and needs no account. For why the correction exists at all, see true solar time in BaZi; to check whether another calculator applies it, try the three test birth times.
Other cities: true solar time in Singapore, true solar time in Kuala Lumpur, true solar time in Vancouver, true solar time in Toronto.