How is change % calculated for Cohort Analysis?

When comparing two different quarters/months/weeks the change % is calculated as follows:

Change = [(Week2 / 7 - Week1 / 7) / Week1 / 7]* 100

For example, let's say we were calculating the change % here where the current date was August 9th.

(13 / 3 - 93 / 7) / 93 /7 *100
= (4.3 - 13.2) / 13.2 * 100
= -8.9 / 13.2 * 100
= -0.67 *1 00
= -67 %

When comparing months/quarters the values should be replaced with the number of days.