How can I make part of date field optional?

[jlrrush]

I have data that may not include complete dates. The month or day may not be known. How can I keep the date/time format but allow the month or date or even the year to stay blank?
For example, 09/_ _/2004 or _ _/_ _/2003

 

[BNPMike]

If you want to store a date it must be a date. 2003 or September 2003 aren't dates. You need to store separate non-date fields, then you can put what you like in them.