How to have one label for multiple select boxes?

Answer 1

You cannot associate a label element with more than one control. This is described in the definition of label.

You could give each select element its own label.

A better approach is to have a single text input field for a date. Then there is no problem with label. It means more work, since you have to parse the data server-side, and you should also parse it client-side (for checks, so that the user can immediately be informed of problems). But it is better usability (surely it is faster to type in a date than to use three clumsy dropdowns) and better accessibility. You need to decide on a date format and clearly tell the user what the expected format is.