I'm creating a Drupal form with a datetime-based javascript popup calendar input that allows users to set a date for when they want to pick something up or drop it off. However, I can't find a way to limit what dates are selectable as input. For example, if we're only open Monday-Wednesday-Friday, I don't want people to be able to use the selector to indicate they want a pickup on Sunday.
I've looked far and low for calendar input validation and a usable blocking mechanism, but so far no luck.