**DETERMINATION OF THE CALENDAR ORDINAL
DATE**

**GIVEN THE CALENDAR WEEK DATE**

**Aristeo Canlas Fernando**

To determine the calendar ordinal date (YYYY-DDD or YYYYDDD) given the calendar week date (YYYY-Www-D or YYYYWwwD), determine first if year is a common year or a leap year. A leap year is a year that is divisible by 4 except century year which should be divisible by 400.

**Common Year**

- Subtract 1 from week number (ww) to get the difference.
- Multiply the difference by 7 to get the product.
- Add product to week day number (D) to get the ordinal date number (DDD).
- Append the ordinal date number to year (YYYY) to get the calendar ordinal date (YYYYDDD).

D is 8 for December 31 only.

**Leap Year **

- Subtract 1 from week number (ww) to get the difference.
- Multiply the difference by 7 to get the product.
- Add product to week day number (D) to get the ordinal date number (DDD).
- If week number is more than 26, add 1 to the sum in step 3 to get the ordinal date number (DDD).
- Append the ordinal date number to year (YYYY) to get the calendar ordinal date (YYYYDDD).

D is 8 for December 31 and June 31 only.

File: findorddate.htm Date first uploaded: 2007 September 3 Rev. 0