Searching For Only Part Of A Date

Ok, so I have a Select statement that looks like this:

Select * from FilteredOpportunity
where (OpportunityID LIKE @opportunityid)
and (Name LIKE @name)
and (CustomerIDName LIKE @customeridname)
and isNull(EstimatedCloseDate, '1900-01-01') LIKE @estimatedclosedate
and isNull(Description, '') LIKE @description
and isNull(AccountIdName, '') LIKE @AccountIDName
and isNull(ACCU_OppTypeName, '') LIKE @ACCU_OppTypeName
and isNull(SalesStageCodeName, '') LIKE @SalesStageCodeName
and isNull(ACCU_CustomerTypeName, '') LIKE @ACCU_CustomerTypeName
and (CreatedByName LIKE @CreatedByName)
and (CreatedOn LIKE @CreatedOn)
and isNull(ACCU_OppSourceName, '') LIKE @ACCU_OppSourceName
and (StateCodeName LIKE @StateCodeName)
and (StatusCodeName LIKE @StatusCodeName)

This chunk of code is used in an XML file which, once this XML is imported (using sharepoint by the way if you haven't noticed), I can then search through tables with different filters. Well, my date filter isn't working the same way as my other ones. I have a couple different date filters, but none of them work.

Before I ask my question, I only pass in one variable at a time through my code.... the rest of the variables get a default value passed to them if the user doesn't pass it. That value is simply '%'. Anyways, so the different ways a user can type in a date is by typing in the whole date, part of the date starting with the beginning of it, typing in the end of the date, or typing something within the date. For a string it's like 'Example', 'Exam%', '%ple', and '%amp% respectively. How do I accomplish this with a date?