Promotions - what are the rules?

[Ben-and-Sam0]

Two things....

1) I have 3 open nights in a row at the end of March and I'd love to set a promotion to try and fill them. But those dates are greyed out. Are there specific rules about how this works, or is it driven by some unknowable variable formula?

2) My calendar says, "3 available promotions," but when I click the box, I just get the option to set a custom promotion. Am I missing something?

Thanks!