When you see the date 7/16/2013, you might see 7th month of the year (6 completed months), 16th day (of a month with 31 days), in the year 2013 (which isn’t a leap year). However, 7/16/2013 is also a number – 41469 – the number of days since 1/1/1900*. Sometimes we can take advantage of the fact that dates are numbers to simplify a date adjustment expression.

If we need bi-weekly or weekly date adjustments in a Data Default (or in a transformation expression and the measurement period isn’t bi-weekly or weekly), then the only way to make these adjustment is to take advantage of the fact that dates are numbers.

* You can’t go into Excel and directly prove this because most versions of Excel incorrectly treat 1900 as a leap year (it’s evenly divisible by 100 but not 400, so it isn’t a leap year). However, if you subtract 1/1/1901 instead of 1/1/1900 and add 365 days for the year 1900 (the number of days in a non-leap year), you will get 41469!