The words year and hour grew from the same ancient root
English year, German Jahr and Old Norse ár all trace back to a Proto-Indo-European word meaning year or season. The same ancestor produced Greek hora, a season or stretch of time, which eventually gave English the word hour. Linguists suspect the root itself came from a verb meaning to go or move.
Many cultures counted years by a single season. People spoke of so many summers, winters or harvests. The old Chinese character for year pictured a person carrying a bundle of wheat, and Slavic languages use a word for summer to mean year as well. Latin annus, a separate root, survives in annual, anniversary and annuity.
Astronomically, a year is Earth's trip around the Sun, and it refuses to divide neatly into days. The tropical year, which tracks the seasons, runs about 365 days, 5 hours, 48 minutes and 45 seconds, while the sidereal year, measured against the stars, is some 20 minutes longer. Every calendar that follows the Sun therefore needs leap days. Julius Caesar's scheme averaged 365.25 days. A Revised Julian calendar proposed in 1923 for some Orthodox churches uses 218 leap years every 900 years and matches the tropical year even more closely than the Gregorian one; the two will first disagree by a day in 2800.
Other traditions went different ways. Lunisolar calendars, such as the Chinese and Hebrew ones, keep twelve lunar months and slot in a thirteenth every three years or so. The Islamic lunar calendar ignores the Sun entirely, so its year is about 11 days shorter. Iran's Solar Hijri calendar places leap days by observation so that Nowruz lands on the spring equinox. Year numbering has its quirks too: there is no year zero, so 1 BC is followed directly by AD 1, and astronomers patch this by calling 1 BC year 0.
Human institutions invent their own years. Canada and India start the fiscal year on 1 April, Australia on 1 July, and the US federal government on 1 October. Britain uses 1 April for corporation tax but 6 April for personal tax. Pupils in American schools typically get 180 teaching days a year, compared with 200 in Australia.
Source: Year
