The Test data you need is that which you enter on the form that you are testing - if you have a form with a date then the date would be one of the test data items.
Also as a new member to the forum I suggest that you read the information sent to you when registered - the subjects of the threads should reflect your question and be meaningful - a thread called "Hi" is not acceptable.
Testers generally input both valid and invalid conditions, so you would input the valid date and a series of invalid dates. I don't know your particular system, so that might be no date, an incorrect date, and several dates input with the wrong format. As you test, think of ways to challenge the system and force errors.
In addition, if you are trying, for example, to verify that Jan 22, 2006 occurs on a Sunday, it stands to reason that your calendar might need to be input first, and perhaps you have parameters which specify business and non-business days. Parameters need to be tested as well.