Month

A month was a unit of time measurement. According to the Fourth Doctor — who was almost certainly speaking of its duration on Earth — a month lasted 2,678,400 seconds. (TV: The Brain of Morbius) As noted by the Ninth Doctor, 12 months made up the Earth year, (TV: World War Three) which was composed of 365 days, 24 hours long. (TV: Last of the Time Lords)

Months had individual names. Known months — not all of which were Earth months, and so not all of which could possibly equal 2,678,400 seconds — included: allowcachedresults=true category=DWU months columns=6

Behind the scenes

 * Though he doesn't specify in the script of The Brain of Morbius, the Doctor's sums reflect a 31-day month.