What’s the best approach to display a month/year filter?

I'm working on an application that allows you to filter your files by month and year. This is what I have so far.

As you can see, the "Apply" button is disabled if fields are empty:

But once the user fills them out, the "Apply" button gets enabled, and a "Clear" button appears so they can clear the form:

• What do you think of this approach?
• Is the year text field clear or do I need to label it yyyy?
• If Month were a label outside the dropdown, what would be its default? "Select month"?