After 163 years, Christmas and Regaip Kandili fell on the same day again.

Gregorian 1862, 25 December Thursday, Hijri 1279, 3 Rajab Thursday.

Calculation Logic 3 things need to happen at the same time:

1) December 25 (fixed date)

-Same date every year in the Gregorian calendar -Christmas day -The date does not change even if the year changes: December 25th in both 1862 and 2025

2) Thursday (7-day cycle)

-The days of the week repeat in a cycle of 7 -December 25th falls on a different day every year -December 25th comes again on Thursday at irregular intervals, such as every 5-6-11 years

3) 1-7th of Rajab. day (shifts in the Hijri calendar)

-The month of Rajab: The 7th month of the Hijri calendar -Regaip Kandili: The first Thursday night of the month of Rajab -The Hijri calendar is 354-355 days old (Gregorian 365 days) -Therefore, the month of Rajab shifts back 10-11 days in the Gregorian calendar every year.