Ok, I know this is a joke, but... in all seriousness, I recently moved FreeBSD releases to a quarterly calendar. The first month of the quarter, people are encouraged to finish up their works in progress and get them into the tree; the second month, we have BETA/RC builds every week; and in the third month (usually at the start but not always) I do the final RELEASE build.

This wasn't for any corporatey reason though; it just happened that "every 3 months" is a natural cadence for doing releases. (In a sense it's a 6-month cadence, like e.g. Ubuntu, but we support two major versions at any given time, and their schedules interleave.)

Sometimes a calendar quarter is just a calendar quarter.