Data type mismatch in criteria expression.

from my code:
SQL

sSQL = "UPDATE tEvents SET rsTitle='"&rsTitle&"', rsName='"&rsName&"', rsCompany='"&rsCompany&"', rsEmail='"&rsEmail&"', rsTelephone='"&rsTelephone&"' WHERE Start_Date = '"&Start_Date&"' AND eventTime = '"&eventTime&"' "


objConn.Execute(sSQL)




when i response.write my SQL I get the following:

UPDATE tEvents SET rsTitle='Mr', rsName='John', rsCompany='biddy', rsEmail='john@john.com', rsTelephone='07939996' WHERE Start_Date = '14/05/2009' AND eventTime = '09:00'