Determination of the day of the week 10 months corresponds to the 2012 calendar year. On the other hand, 2019 is a common year starting on Tuesday, meaning that 2019 corresponds to the 2013 calendar year. 2020 is a leap year starting on Wednesday, meaning that 2020 corresponds to the 1992 calendar year, meaning that the first two months of the year begin on the same day as they do in 2014 (i.e. January 1 is a Wednesday and February 1 is a Saturday) but because of a leap day the last ten months correspond to the last ten months in 2015 (i.e. March 1 is a
Determination of the day of the week the intended design objective. The tabular forerunner to Tøndering's algorithm is embodied in the following K&R C function. With minor changes, it was adapted for other high level programming languages such as APL2. Posted by Tomohiko Sakamoto on the comp.lang.c Usenet newsgroup in 1992, it is accurate for any Gregorian date. IBM's Rata Die method requires that one knows the "key day" of the proleptic Gregorian calendar i.e. the day of the week of January 1, AD 1 (its first date). This has to be done to establish the remainder number based on which the day of the week is