Assuming it's a DateTime value, then it's simple:
DateTime.Date[
^] discards teh time portion, so the comparisons would be date only.
But that doesn't involve any conversions, so I suspect that you are trying to compare strings as dates and getting problems. Don't do that: convert your dates to DateTime and use them - the chances are that you have stored dates in you DB as strings, and as a result some of them are in incompatible formats, or just plain wrong. We can't help you there - you will have to fix your db design first and then convert your data.