1. (in England, Ireland, and Wales) one of the four days, Lady Day, Midsummer Day, Michaelmas, or Christmas, regarded as marking off the quarters of the year, on which quarterly payments are due, tenancies begin and end, etc.
2. (in Scotland) one of the four days, Candlemas, Whitsunday, Lammas, or Martinmas, regarded as marking off the quarters of the year.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.