Year

A year was a unit of time equivalent to one full solar rotation, which differed from planet to planet. (AUDIO: The Resurrection of Mars)

Measurements
An "Earth Year" (PROSE: Who Am I?) typically lasted 365 days, each 24 hours long, across 12 months. (TV: World War Three, Last of the Time Lords) More specifically, in an Earth-standard Gregorian calendar, a year was 365.25 days long. (PROSE: Instead of You) Earth and Gallifrey shared the same distance from the same type of sun and with it the same length of day and year, a fact which fascinated the Time Lords. (PROSE: The Infinity Doctors) According to another account, the Fourth Doctor once said to a human audience that he "would be over 750 years old in your Earth years", suggesting the years of his homeworld had a different length. (PROSE: A Letter from the Doctor)

A Yquatine year consisted of 417 days, divided into ten months of about 42 days each, further divided into four seasons. (PROSE: The Fall of Yquatine)

A night on Darillium lasted 24 Earth years. (TV: The Husbands of River Song)

The Sontarans measured time with Sontaran martial years. (AUDIO: Heroes of Sontar) On Manussa, time was measured with Manussan years. (AUDIO: The Cradle of the Snake, TV: Snakedance)

The Space Year was a standard human dating system used by colonists on Destination, (AUDIO: The Destination Wars) among other worlds. (TV: Genesis of the Daleks)

Annual events
Beltane was a pagan festival which began at midnight on 30 April — that is, the first minute of the first day of May. 1 May itself was May Day. (TV: The Dæmons)

August bank holiday was described by the Seventh Doctor as a "silly pagan festival". (PROSE: Lungbarrow)

According to the Fourteenth Doctor, the "whole idea" of an annual was that it was yearly, and so the year his previous letter to the annual's readers was appropiate. He also asked the readers about their year and mentioned that his had "its ups and downs." (PROSE: )