January Facts

January at a glance

Why is January called January?

January is named after Janus, the Roman god of beginnings, gates, doorways and transitions. The Latin name was Ianuarius, short for mensis Ianuarius, "the month of Janus," and the English word January comes from it.

Janus was shown with two faces looking in opposite directions, often read as one face on the past and one on the future. That made him a fitting patron for the month that opens the year. His name is related to the Latin word ianua, "door."

Romans called on Janus at the start of prayers and rituals, before other gods. The gates of his shrine in the Roman Forum stood open in wartime and were closed only when Rome was at peace; Augustus recorded that they were shut three times during his rule.

Why is January the first month?

The earliest Roman calendar, traditionally credited to Romulus, had 10 months and began in March. That is why September, October, November and December are named after the Latin numbers for seven to ten. According to Roman tradition, King Numa Pompilius added January and February around 713 BC to bring the calendar closer to the lunar year. In this pre-Julian calendar, January had 29 days.

From 153 BC, Rome's two consuls, its chief annual magistrates, took office on January 1. Romans identified each year by the names of its consuls, so January 1 became the start of the civil year. Julius Caesar's reform of 46 BC, which created the Julian calendar used from 45 BC, kept that starting point and lengthened January to 31 days.

The start of the year was not settled everywhere after Rome. Many parts of medieval Europe began the year on Christian feast days such as December 25 or March 25. In England the legal year began on March 25 until the Calendar (New Style) Act 1750 moved it to January 1 from 1752, in England and its colonies, including those in America; Scotland had already made the change in 1600. Today January 1 is New Year's Day under the Gregorian calendar, introduced by Pope Gregory XIII in 1582 and now the world's main civil calendar.

How many days are in January?

January always has 31 days, in common years and leap years alike. That is four full weeks plus three extra days, so three days of the week occur five times in every January. In 2027, January begins on a Friday and ends on a Sunday, so Friday through Sunday each appear five times, and the month has 21 weekdays. See January working days for US and UK counts by year.

January's calendar repeats in predictable ways. In a common year it starts on the same weekday as October, because the 273 days from January 1 to October 1 make exactly 39 weeks. In a leap year it matches April and July instead. A common year also begins and ends on the same weekday, since 364 days is exactly 52 weeks.

January 31 is day 31 of the year, with 334 days remaining in a common year and 335 in a leap year. Under the ISO 8601 week system, week 1 is the week containing the year's first Thursday, so January 1–3 can belong to the last week of the previous year; see January week numbers.

January abbreviation and month number

The standard abbreviation for January is Jan. The three-letter form JAN, without a period, is common on forms, tickets and in computing. Associated Press style, used by many US newsrooms, abbreviates January only with a specific date, as in Jan. 15, and spells it out when it stands alone or with just a year.

In numeric dates January is month 1, written 01 in two-digit formats. January 15, 2027 is 2027-01-15 in the international ISO 8601 format, 1/15/2027 in the usual US order, and 15/01/2027 in the day-first order used in the UK, India, Australia and much of the world.

January astronomy and seasons

Earth reaches perihelion, its closest point to the Sun, in early January, usually between January 2 and January 5. It is then about 91.4 million miles (147.1 million km) from the Sun, roughly 3 million miles closer than at aphelion in early July. Seasons come from the tilt of Earth's axis, not its distance from the Sun, which is why the Northern Hemisphere has winter at perihelion.

The Quadrantid meteor shower peaks around January 3–4. Under dark skies it can be one of the strongest showers of the year, but its peak lasts only a few hours. The name comes from Quadrans Muralis, an old constellation that is no longer recognized.

A lunar cycle lasts about 29.5 days, so January always has at least one full moon and occasionally two. January's full moon is often called the Wolf Moon. The 2027 January full moon falls on Friday, January 22, 2027; the January full moon page lists dates and times for every year.

January is midwinter in the Northern Hemisphere and, on average, the coldest month of the year across much of the United States and Canada. In the Southern Hemisphere it is midsummer: in Australia and New Zealand, January falls within the long school summer break.

January symbols and traditions

Separate guides cover the January birthstone, the January birth flowers and the January zodiac signs, including why the Capricorn–Aquarius changeover can shift by a day.

"Blue Monday," billed as the most depressing day of the year, is a marketing invention. It began with a 2005 press release in the UK that was issued to promote travel, and its "formula" has no scientific basis. It is now usually placed on the third Monday of January, which in the US is Martin Luther King Jr. Day.

Dry January, a month without alcohol, began as a public campaign by the UK charity Alcohol Concern, now Alcohol Change UK, in 2013.

Related

• Birthstone: garnet
• Birth flowers
• Zodiac signs
• Full moon (Wolf Moon)
• January in other languages
• Days of January
• January 2027 calendar