:confused: Is it legal for an employer to block off the last two weeks of every month so no one in the office can take vacations during those times? I am not sure if this is allowed.

Yes, it is legal. In every state. Employers don't have to approve every vacation request that comes down the pike.

but are they allowed to block periods of time each month ???

Yes, it is legal to to block periods of time each month.

In fact, it's legal for the company to not provide any vacation at all, to anyone.

They could, and many companies do, block out 50 weeks out of the year and say that EVERYONE has to take their vacation at the same time, no matter what.

No law in any state dictates to an employer how they have to allow vacations. It is entirely up to the employer, in every states, whether to provide paid vacation at all and if so, when an employee is allowed to take it.