Two cycles, one named calendar
HKO describes the Chinese calendar as lunar months coordinated with the seasonal solar cycle. Its months contain 29 or 30 civil days; a leap year contains an additional month. The solar terms describe a separate sequence through the tropical year.
What the three Atlas references answer
Entered local date asks for a lookup of the supplied Gregorian date in the modern Chinese reference calendar. China date first converts the supplied instant to a date at fixed UTC+08, then looks up that date. Neither option recomputes lunar months for the birthplace meridian.
Li Chun solar year is a different question: it selects the year using the calculated 315° solar boundary. That row does not supply a lunar month or day. A solar year and a lunisolar date can be useful together without being the same output.
Worked comparison · one instant, two civil dates
Use the original Atlas example 9 February 2024 at 17:00 in America/New_York. The resolved instant is 22:00 UTC that day and 06:00 on 10 February at UTC+08. The entered-local-date lookup still belongs to the 2023 lunar year; the China-date lookup has reached the 2024 lunar year.
The February almanac places Lunar New Year on 10 February and Spring Commences on 4 February. Thus the example’s Li Chun year is also 2024 under the separately declared solar-year rule. Its agreement with the China-date year is specific to this instant.
HKO · February 2024 almanac, year and solar-term boundaries ↗
Use only the information actually recorded
With a date but no birth time, use the date-only lookup. Its receipt preserves the entered date and keeps moment-based China-date and Li Chun comparisons unavailable. If a recorded uncertainty interval crosses civil dates, the displayed date result cannot represent every possible instant in that interval.
Save the method and reference together with the result. Historical calendar reforms and other regional lunisolar systems require their own rules; this tool does not establish their dates by changing a place name.
What the published tables can verify
The explorer supports 1901–2100 and has selected independent reference checks. HKO’s conversion tables cover those years, but table coverage is not proof that every engine output has been certified. HKO also warns that future astronomical events close to midnight can produce a one-day calendar discrepancy.
For a consequential comparison, inspect the named reference date, leap marker and original source table. A matching date verifies a calendar correspondence within that scope; it does not verify a personality or event prediction.
Word origin · etymology
Latin-derived scientific compound.
Luni- comes from luna, Moon, and solar from sol, Sun; the compound names calendar rules using both cycles.
How we know · epistemology
Rule-based astronomical calendar
Month starts and intercalation rules connect lunar cycles with the solar year. Calendars can differ through reference meridians and adopted rules even when using the same sky, so conversion requires naming the calendar rather than only its broad type.
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Connected concepts
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Terms used in this explanation
Mentioned in 2 other entries
These links connect subjects and terminology. They do not establish a shared historical origin.
Sources & provenance
Use the citations beside each section to distinguish a calculation convention, a historical teaching and an editorial example.