You can bid for vacation. You can also choose not to bid. The company will randomly assign your maximum vacation days... Upon your return, and within 30 days, you may cancel the awarded vacation and either bid monthly vacation or request your assigned dates be moved to any date that was awarded to a junior pilot.

Ref: MOU 24 (page 637 of the UPA)

I emailed the company and had mine moved. Worked like a champ.