2019.10.18 in #430Perl Weekly Challenge: Week 30
Jaldhar shared really nice tricks with regard to the Christmas day task. "Christmas always falls on December the 25th which is exacly one week before New Years Day of the next year. So if we know the next New Years Day is on a Sunday, we know Christmas is on a Sunday. How do we know which day of the week New Years Day is on? Well, January 1, 2019 was on a Tuesday. January 1, 2020 will be on the next consecutive day of the week i.e. Wednesday. For each subsequent year we increment the day of week by one. The only stumbling block is for leap years which have an extra day. So for the year after a leap year, we have to increment by two."