Saint Luke's summer

Word Origin for Saint Luke's summer

referring to St Luke's feast-day, Oct 7 in the pre-Gregorian calendar (now Oct 18)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012