This report prints all people whose birthday appears during the provided month. Note the Ignore year portion of date checkbox on the Date of birth filter: it tells VSys to only look at the month and day portion of the dates when filtering people.
For birthdays in February, use "2000" as the year. Why? It's a leap year, and to get those people born on February 29th, you can't use a non-leap year and still be able to specify that day! (Any other leap year will work, too.)