Chinese festivals are commonly described as falling on lunar dates, and most of them do. Lunar New Year is the first day of the first month; Dragon Boat is the fifth of the fifth; Mid-Autumn is the fifteenth of the eighth.
Two of the best-known are not lunar at all. Qingming and the Winter Solstice are fixed by the sun, and a converter that treats them as lunar dates will produce the wrong day. So will a person.
One statute separates them in a single article
Taiwan's act on commemorative days and festivals, promulgated in May 2025, sets out the festivals in a single article, and the pattern is visible in the article itself: Lunar New Year is given as the first day of the first lunar month, Dragon Boat as the fifth day of the fifth, Mid-Autumn as the fifteenth day of the eighth — and Qingming is given as "the day of Qingming".
The statute does not assign Qingming a lunar date because it has none to assign. Qingming is a solar term, and its date is decided by where the earth is in its orbit.
The Hong Kong Observatory states the mechanism plainly: the twenty-four solar terms divide the ecliptic into twenty-four equal segments, fifteen degrees of solar longitude apart. Qingming is the term at fifteen degrees. The Winter Solstice is the one at two hundred and seventy.
What that does to the two dates
Because they are solar, these festivals barely move against the Gregorian calendar and move enormously against the lunar one. The Observatory's conversion tables for 1901 to 2100 make the asymmetry concrete.
Qingming takes exactly three Gregorian dates across two centuries: 4 April in seventy-four years, 5 April in a hundred and five, 6 April in fourteen. Against the lunar calendar it takes thirty-two distinct dates, spread across two different lunar months.
The Winter Solstice behaves the same way — 21, 22 or 23 December, and always somewhere in the eleventh lunar month, on thirty different days of it.
A couple of those Gregorian values are effectively historical. The last 6 April Qingming was in 1943; the last 23 December solstice was in 1951, and 21 December did not occur at all until 1988, after which it became common. The drift is the leap-year rule slowly catching up with the orbit.
A claim repeated by a lot of official outlets, and it is not right
State and municipal news outlets across the mainland often claim that Qingming is the only one of the twenty-four solar terms that is also a festival. This is false.
The narrower version — that Qingming is the only solar term that is a statutory holiday — is true of the mainland and false a short distance away. Hong Kong names the Winter Solstice in employment law: its statutory holidays include "the Chinese Winter Solstice Festival or Christmas Day, at the option of the employer". The solstice has been in that list since Hong Kong's statutory holidays were first set out, when all of them were Chinese festivals.
In Hong Kong a solar term is a statutory day off, which an employer may give instead of Christmas.
Hong Kong in 2026, where two astronomies meet in one statute
The clearest illustration of what solar dating does to law is next year.
Qingming 2026 falls on Sunday 5 April. Hong Kong's rule substitutes the following day. But the following day is Easter Monday, which is already a holiday — and Easter is fixed by a completely different computation, one built on the ecclesiastical moon and the vernal equinox rather than on solar longitude.
The government's own notice explains the cascade: because Qingming falls on a Sunday the following day is substituted, and because that day is itself already a general holiday, the next day that is not becomes an additional one. The result is four consecutive holidays, on 3, 4, 6 and 7 April, produced by a Chinese solar term colliding with the Christian computus and resolved by a single statutory sentence.
The same statute holds another trap for converters. Hong Kong does not make Mid-Autumn itself a holiday. The statutory item is "the day following the Chinese Mid-Autumn Festival", because the festival is celebrated at night. A tool that maps the festival to the holiday will be one day early every year.
When the almanacs disagreed, and someone had to decide
Solar and lunar boundaries are instants, not days, and an instant close to midnight can put two competent calculations on different dates.
In 1978 the new moon that began the eighth lunar month fell at nine minutes past midnight on 3 September, Hong Kong time. The Observatory and the mainland's Purple Mountain Observatory both placed the first of the month on 3 September, which put Mid-Autumn on 17 September. Hong Kong's commercially printed almanacs, still using an older method carrying a few minutes of error, placed it on 2 September and printed Mid-Autumn as 16 September.
Hong Kong had two Mid-Autumn dates in circulation in the same year. The Observatory intervened in its official timekeeping capacity to confirm the correct one, and afterwards sent staff to Nanjing to learn calendar compilation.
A version of this story circulates in which the dispute was between the Observatory and the mainland, over which meridian to use. That is not what happened — the two observatories agreed. The disagreement was with the commercial almanac trade.
The Observatory publishes a list of the days it might be wrong about
The 1978 case is more than an anecdote because the Observatory still treats the risk of midnight boundaries as an ongoing problem.
Its conversion pages warn that dates for a new moon or a solar term falling close to midnight may differ by a day, and the observatory lists the specific dates at risk. Among the solar terms flagged is the Winter Solstice of 2021, which fell at 23:59:06 Beijing time. Fifty-four seconds earlier in the day and the eleventh lunar month, which is defined as the month containing the solstice, would have been a different month.
These calendars are decided at that level of precision, which is why the authority publishing the table matters as much as the arithmetic.
One more thing a converter can get wrong: New Year's Eve
Lunar New Year's Eve is often assumed to be the thirtieth day of the twelfth month. It frequently is not, because the twelfth month is only twenty-nine days long in about forty per cent of years — seventy-nine of the two hundred in the Observatory's tables.
In those years there is no thirtieth day at all, and the eve is the twenty-ninth. We are in the middle of a five-year run of exactly that, from 2025 through 2029, and the State Council's own holiday notice for 2026 identifies the eve as the twenty-ninth day of the twelfth month.
This matters more now that the eve is a public holiday on the mainland, a change made by a 2024 revision that took effect in 2025.
What a tool should do, and what ours does
The correct treatment is to store the solar-term festivals without a lunar date at all and resolve them from solar longitude, rather than storing an approximate lunar date and converting.
That is what our lunar festival calendar does: Qingming and the Winter Solstice carry no lunar month or day and are resolved as solar terms, and the New Year's Eve case falls back from the thirtieth day to the twenty-ninth when the month is short. Storing 清明 as a lunar date is the specific mistake this guide is about, so a worked example of the alternative seemed worth including.
Where this comes from, and what will date it
The Taiwanese statute is the 2025 act as published by the government's law database. The solar-term mechanism, the two hundred years of conversion tables and the midnight-boundary warnings are all the Hong Kong Observatory's. The Hong Kong statutory holidays are from the Labour Department's guide and the government's published holiday notices for 2026 and 2027. The mainland holiday arrangements are from the 2024 State Council decree and the 2026 notice.
The two-century counts were computed from the Observatory's published files rather than taken from a summary, so they can be reproduced by anyone willing to read two hundred text files.
This guide will be dated by changes in statutes, not astronomy. Taiwan's act was a 2025 replacement for an earlier one, and holiday arrangements are revised regularly. The solar terms will not move; which days a government declares a holiday will.
