Date and Time Criteria Expressions [Access 2003 VBA Language Reference]
To specify date or time criteria for an operation, you supply a date or time value as part of the string expression that forms the criteria argument. This value must be enclosed in number signs (#).
Note The number signs indicate to Microsoft Access that the criteria argument contains a date or time within a string.
Suppose that you are creating a filter for an Employees form to display records for all employees born on or after January 1, 1960. You could construct the criteria argument for the form's Filter or ServerFilter property as in the following example. Note the placement of the number signs.
Forms!Employees.Filter = "[BirthDate] >= #1-1-60#"