January 1

January 1 is the first day of the year in the Gregorian calendar. There are 364 days remaining until the end of the year (365 in leap years).

History

During the Middle Ages under the influence of the Catholic Church, many countries in western Europe moved the start of the year to one of several important Christian festivals – December 25 (the Nativity of Jesus), March 1, March 25 (the Annunciation), or even Easter. Eastern European countries (most of them with populations showing allegiance to the Orthodox Church) began their numbered year on September 1 from about 988.

In England, January 1 was celebrated as the New Year festival, but from the 12th century to 1752 the year in England began on March 25 (Lady Day). So, for example, the Parliamentary record notes the execution of Charles I as occurring on January 30, 1648, (as the year did not end until March 24), although modern histories adjust the start of the year to January 1 and record the execution as occurring in 1649.

Most western European countries changed the start of the year to January 1 before they adopted the Gregorian calendar. For example, Scotland changed the start of the Scottish New Year to January 1 in 1600. England, Ireland and the British colonies changed the start of the year to January 1 in 1752. Later that year in September, the Gregorian calendar was introduced throughout Britain and the British colonies. These two reforms were implemented by the Calendar (New Style) Act 1750.

Unix time

Unix time (also known as POSIX time or Epoch time) is a system for describing instants in time, defined as the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970, not counting leap seconds. It is used widely in Unix-like and many other operating systems and file formats. Because it does not handle leap seconds, it is neither a linear representation of time nor a true representation of UTC. Unix time may be checked on most Unix systems by typing date +%s on the command line.

Definition

Two layers of encoding make up Unix time. These can usefully be separated. The first layer encodes a point in time as a scalar real number, and the second encodes that number as a sequence of bits or decimal digits.

As is standard with UTC, this article labels days using the Gregorian calendar, and counts times within each day in hours, minutes, and seconds. Some of the examples also show International Atomic Time (TAI), another time scheme, which uses the same seconds and is displayed in the same format as UTC, but in which every day is exactly 86400 seconds long, gradually losing synchronization with the Earth's rotation at a rate of roughly one second per year.