Winter is one of the four seasons that make up the year. It is the coldest time of the year and falls between autumn
) and spring
, the intervening periods that lead from and to summer
, the warmest time of the year.
Astronomical winter vs. meteorological winter
There are various ways to define the start and end dates of winter. The two most commonly used ones are based on the astronomical calendar and the meteorological calendar. Astronomical and meteorological winter start and end on different dates.
In the astronomical calendar the start and end dates of winter are based on the changing position of Earth in relation to the sun and the resulting solar events of equinoxes and solstices. In the Northern Hemisphere autumn ends and winter starts at the moment of the December solstice
, which occurs every year between December 20 and December 23. Winter ends and spring starts at the moment of the March equinox
, which occurs every year between March 19 and March 21. In the Southern Hemisphere winter lasts from the June solstice
(June 20 to 22) to the September equinox
(September 21 to 24).
The start and end dates for winter given on this page are the dates of astronomical winter in the Northern Hemisphere and are based on Coordinated Universal Time (UTC), which for practical purposes is equivalent to Greenwich Mean Time (GMT - the time zone of the United Kingdom). While winter starts and ends at the same moment in time all over the Northern Hemisphere, the date and local time differ from place to place depending on the year and a location's time zone. For locations that are ahead of UTC (further east) it may fall on the day after, and for locations that are behind UTC (further west) it may fall on the day before. To find out the exact date and time of winter 2021 in your area use this seasons calculator
Meteorologists, on the other hand, define seasons based on climatic conditions and the annual temperature cycle. It is important for them to be able to compare the same period of time in different years. The length of the astronomical seasons varies between 89 and 93 days, while the length of the meteorological seasons is less variable and is fixed at 90 days for winter in a non-leap year (91 days in a leap year
), 92 days for spring and summer, and 91 days for autumn. While the exact definition of a season's timing and length can differ in different areas based on local conditions, in most of the Northern Hemisphere meteorological winter is generally defined as the three months of December, January and February, with the season starting on December 1 and ending on February 28 (29 in a leap year).
There is no "official rule" which definition of winter to use, and different countries adhere to different conventions. Most of North America and Europe use astronomical winter, while Australia and New Zealand use meteorological winter (however, as these countries are in the Southern Hemisphere, the seasons are opposed and winter there lasts from June to August). In other cultures, eg. in the traditional Chinese calendar and in Celtic traditions, the December solstice is considered to be roughly the middle of winter.
Comparison table: meteorological spring vs. astronomical spring
Dates shown apply to the Northern Hemisphere and are based on UTC (GMT)
2021 calendar as templates for
Word, Excel and PDF
A selection of calendar templates for 2021 in landscape and portrait orientation and with US federal holidays, suitable for a variety of applications.