Im using openerp 7 and in the holiday module i have a requirement of comparing two dates literally but technically they are two diferent data types. Simply i want to collect all the employee who had applied leave for a back date. In the table there are two different columns as 'date from' (which is the applying leave date, may be a backdate) and request_confirm_date (which will record the current time stamp). So when a back date is applied as leave its request confirm date is the current time. So by comparing the logic 'date_from' <'request_confirm_date' i can fetch the employee. 
Here the problem is date_from is a datetime and request_confirm_date is a character.

In the xml i tried the following code and its say 'Cannot read property 'length' of undefined'

Here the code,

<filter name = "Leave Filters" string = "Leave Filters" domain = "[('date_from', '&lt; =', ((request_confirmed_date.strftime ('%% Y - %% m - %% d')) )] "/>

Uncaught TypeError: Cannot read property 'length' of undefined