Quarter Days, in England and Ireland Lady Day, 25th March; Midsummer Day, 24th June; Michaelmas Day, 29th September; and Christmas Day, 25th December; while in Scotland the legal terms are Whitsunday, 15th May, and Martinmas, 11th November, though the Whitsunday term is now changed to the 28th May.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Quarles, Francis * Quarter-deck