Calculating future occurrences of Friday the 13th

Question

I\'d like to be able to start with a year, and calculate occurrences of Friday the 13th. A brute force solution is easy and obvious. I have something slightly better, but

Answer 1

This is how I would do it:

• Assume year is known and is an integer.

• Loop from 1 to 12

  • Create date with loop index, year and 13 for the day

    • Determine day of week as per established algorithms

    • If day of week calculated above is Friday, do your work

If you want to start with a month and year (you have to assume some sort of year), your algorithm becomes

• Assume year is known and an integer

• Assume month is known and is an integer

• Loop

  • Create date with index of loop as year, known month variable, and 13 for the day

  • Determine day of week as per established algorithms

  • If day of week calculate above is Friday, return date, else

  • Else increment year by 1