Friday the 13^th – Leap Year

	Days to the 13th	Sun	Mon	Tues	Wed	Thurs	Fri	Sat
13-Jan	13	6	0	1	2	3	4	5
13-Feb	44	2	3	4	5	6	0	1
13-Mar	73	3	4	5	6	0	1	2
13-Apr	104	6	0	1	2	3	4	5
13-May	134	1	2	3	4	5	6	0
13-Jun	165	4	5	6	0	1	2	3
13-Jul	195	6	0	1	2	3	4	5
13-Aug	226	2	3	4	5	6	0	1
13-Sep	257	5	6	0	1	2	3	4
13-Oct	287	0	1	2	3	4	5	6
13-Nov	318	3	4	5	6	0	1	2
13-Dec	348	5	6	0	1	2	3	4

This table is for a year that is a leap year. This table shows the mod 7 value for the 13^th of the month for each month. If it occurs on a Friday the value will be 6, which corresponds to 6 mod 7. The day at the top of the table is the day on which January 1 fell. We can see from the table that each month has at least one Friday the 13^th. If January 1 falls on Sunday during a leap year, there will be three months that the 13^th falls on Friday. During a leap year there will be no consecutive months that have a Friday the 13^th since February now has 29 days which is not an even multiple of 7. Thus, the days in March will now fall on different days than those in February, which is the only possibility for having consecutive days in a non leap year. After a leap year the starting day for the next year’s calendar will be the previous year’s starting day plus 2. This table was also made on Excel using the mod 7 formula.