In addition to the advice above - which I believe merits repetition since it's clearly part of your whole life as well as your writing style: DON'T SHOUT. Using all capitals is considered shouting on the internet, and rude (using all lower case is considered childish). Use proper capitalization if you want to be taken seriously.
See how annoying that could be? DON'T SHOUT. USING ALL CAPITALS IS CONSIDERED SHOUTING ON THE INTERNET, AND RUDE (USING ALL LOWER CASE IS CONSIDERED CHILDISH). USE PROPER CAPITALIZATION IF YOU WANT TO BE TAKEN SERIOUSLY.
It's rude. So stop doing it. Seriously.
The first thing to do is to fix your whole app, not just that fragment. Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.
When you concatenate strings, you cause problems because SQL receives commands like:
SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'
The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:
SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;
Which SQL sees as three separate commands:
SELECT * FROM MyTable WHERE StreetAddress = 'x';
A perfectly valid SELECT
DROP TABLE MyTable;
A perfectly valid "delete the table" command
And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.
So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?
In this case, the use of concatenation could easily be causing your problem, as you are forcing a date format on a system which has to interpret that string-based date as a DATETIME object - and that means making assumptions about the format from the system settings which may not match the format you have decided is "right". If it doesn't match, the DB will reject the SELECT and that may be the problem you have seen.
Fix it through your whole app, and the problem may go away.
Oh, and by the way: STOP SHOUTING