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Webster 1828 Edition

Noun.

The day that completes three months, the quarter of a year; the day when quarterly payments are made of rent or interest.

See also: quarter day

quarter-day ‎(plural quarter-days)

(Britain) Each of the four days customarily regarded as starting a new quarter year, on which rents etc are often due.
- 1908, It is late in March, so quarter-day is at hand. — Arthur Conan Doyle, ‘The Adventure of Wisteria Lodge’ (Norton 2005, p. 1239)

each of four days on which rents due

in England: Lady Day (25 March), Midsummer Day (24 June), Michaelmas (29 September), Christmas Day (25 December).
in Scotland: Candlemas (2 February), Whitsun (15 May), Lammas (1 August), Martinmas (11 November).