Today in other calendars

The Hebrew calendar is the official calendar of the State of Israel and the calendar of Jewish religious life. It is lunisolar: months follow the Moon, and a thirteenth month is added in 7 of every 19 years (years 3, 6, 8, 11, 14, 17 and 19 of the cycle) to keep Passover in spring. Since the fourth century it has been fixed by calculation rather than observation.

The year begins on 1 Tishrei (Rosh Hashanah). Its start is set from the mean new moon (the molad), counted in hours of 1,080 parts, and then postponed by a day or two under four rules so that, among other things, Rosh Hashanah never falls on a Sunday, Wednesday or Friday. As a result a common year has 353, 354 or 355 days and a leap year 383, 384 or 385. In a leap year the month Adar is doubled into Adar I and Adar II.

Our dates use the arithmetic rules published by Dershowitz and Reingold, which give the same results as the Unicode ICU library and the Hebcal service. A Hebrew day begins at sunset, so an evening event can belong to the next Hebrew date; the converter shows the date for the daytime.

Rosh Hashanah

The Chinese calendar (农历) is also lunisolar, and China’s national standard GB/T 33661-2017 sets how it is computed. Each month begins on the day of the new moon in Beijing time. The month that contains the winter solstice is the 11th month, and the year’s first month, the start of the Spring Festival, is the second month after it, not counting a leap month. When a year has 13 months, the first month after the winter solstice that contains no principal solar term becomes a leap month, repeating the number of the month before it. Chinese New Year therefore falls between January 21 and February 21.

Years are named in a 60-year cycle that pairs ten heavenly stems with twelve earthly branches, the branches being the familiar animals. 2026 is a Bing-wu year, the year of the Horse; 2027 is Ding-wei, the Goat.

We compute lunar dates from a month table for 1901–2100, checked day by day against the Hong Kong Observatory’s official conversion tables for 1990–2060 with no difference. Software that computes new moons itself can disagree when a new moon falls within minutes of midnight in Beijing: the new moon of February 6, 2027 at 23:56 Beijing time makes Chinese New Year February 6, not February 7. The Observatory notes that new moons and solar terms falling close to midnight decades ahead carry a few minutes of uncertainty, so a few far-future months may shift by a day when officially published.

Chinese New Year

The Solar Hijri calendar is the official calendar of Iran. It is a solar calendar: the year begins with Nowruz, the March equinox, and its first six months have 31 days, the next five 30, and the last, Esfand, 29 or 30. Years are counted from the Hijra like the Islamic calendar, but in solar years, so 2026 corresponds mostly to 1405.

Officially, Nowruz is set astronomically: it is the day of the equinox if the equinox comes before true noon on Iran’s reference meridian (52.5° E), otherwise the next day. Leap years follow from that rule, usually every four years and sometimes after five. We compute the calendar with a 33-year arithmetic cycle. It agrees with the University of Tehran Calendar Center’s published Nowruz dates for 1404 and 1405, and with the astronomical rule applied to the US Naval Observatory’s equinox times for every year from 1394 to 1429 (2015–2050). Arithmetic cycles drift from the astronomical rule over centuries, so for far past or future years the official rule is authoritative.

Nowruz (1 Farvardin)

1404 and 1405 match the Calendar Center’s published dates; later years are computed and match the astronomical rule with USNO equinox times.