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24 Solar Terms Calculator (二十四节气)

Lists the 24 solar terms (节气 jieqi) of a Gregorian year with their exact instants: the moments the Sun's apparent longitude reaches multiples of 15°, computed astronomically and shown in a chosen UTC offset (China Standard Time by default).

When to use

You need the date or time of 立春, 清明, 夏至, 冬至 or any other solar term in a given year, or the full 24-term table.

Do not use when: You only need the term that a specific date falls in (use lunar-calendar-converter), or you need sunrise/sunset times (use sunrise-sunset).

Formula

term instant: apparent geocentric solar longitude λ(JDE) = k·15° for k = 0 (春分) … 23 (惊蛰), solved by Newton iteration; UT = TT − ΔT; local time = UT + utc_offset_hours

Solar longitude from the VSOP87 series subset in Meeus (the series also used by the NREL SPA) with nutation and aberration, ΔT from the Espenak–Meeus polynomials; accuracy about ±1 minute (larger far from the present because ΔT is extrapolated), matching the Hong Kong Observatory times to the minute for the checked years. Times are rounded to the minute. Traditional calendar/cultural reference calculation; not a prediction, medical, legal or financial advice.

Inputs

ParameterTypeUnitRequiredDescription
yearintegeryesGregorian calendar year (1900–2100). Range: ≥ 1900, ≤ 2100
utc_offset_hoursnumberhdefault 8Fixed UTC offset in hours for the local date-times (8 = China Standard Time; 9 = Japan/Korea; 5.5 = India). Range: ≥ -12, ≤ 14

Outputs

OutputTypeUnitDescription
termslist24 rows in calendar order (小寒 first): name_cn, pinyin, english, solar_longitude (°), datetime_local, datetime_utc, date, type (major 中气 / minor 节).
lichun_datestringLocal date and time (HH:MM) of 立春, the start of the solar-term year.
spring_equinoxstringLocal date and time of 春分 (Sun at 0°).
summer_solsticestringLocal date and time of 夏至 (90°).
autumn_equinoxstringLocal date and time of 秋分 (180°).
winter_solsticestringLocal date and time of 冬至 (270°).
year_ganzhistringSexagenary name of the year with pinyin and element/animal.
suishou_notestringWhen the sexagenary year begins under solar-term reckoning (立春) versus the lunar calendar (Chinese New Year).
utc_offsetstringOffset applied to datetime_local and date.

Example

2024 (China Standard Time): {"year":2024,"utc_offset_hours":8} → {"lichun_date":"2024-02-04 16:27","winter_solstice":"2024-12-21 17:20","summer_solstice":"2024-06-21 04:51","spring_equinox":"2024-03-20 11:06"}

2026 立春: {"year":2026,"utc_offset_hours":8} → {"lichun_date":"2026-02-04 04:02"}

GET https://tttkmbb.com/api/v1/calculate/solar-terms?year=2024&utc_offset_hours=8

Machine access

Sources

FAQ

Why do some sources give a different date for a term?

The date depends on the time zone: a term at 00:30 Beijing time falls on the previous day in UTC. Published Chinese almanacs use UTC+8, which is the default here.

What is the difference between 节 and 中气?

The 24 terms alternate: the 12 minor terms (节, odd multiples of 15°: 立春, 惊蛰 …) start the sexagenary months; the 12 major terms (中气, even multiples: 雨水, 春分 …) fix the lunar month numbers and decide which month becomes a leap month.

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