In addition to what Vince Angelo wrote, below an example of an expression for data in an Enterprise GDB (Oracle) and the same data in a File GDB:
EGDB (data resides in Oracle):
YourDateField BETWEEN timestamp '2014-02-16 16:53:25' AND timestamp '2014-02-17 18:53:25'
FGDB:
YourDateField BETWEEN date '2014-02-16 16:53:25' AND date '2014-02-17 18:53:25'
The whereclause parameter would become:
where_clause="YourDateField BETWEEN timestamp '2014-02-16 16:53:25' AND timestamp '2014-02-17 18:53:25'"
More on this in the help topic: "SQL reference for query expressions used in ArcGIS"
scroll down to Date-time syntax for ArcSDE geodatabases