Timestamps in oracle are not text - their representation
on screen is. Dates are just like that, but have less
resolution (1 second for date, 1 nanosecond (10^-9 sec)
for a timestamp).
Having said that - the representation depends on what
format you have defined to show timestamps in. There's
always a default, so you'll always see 'something'.

Relying on the default format mask is a dangerous thing
to do - therefor, always do an explicit conversion:
select * from table
where timestamp = to_timestamp(date.text,'format_mask');
format_mask is the generic text representation of how
your Date.text looks like.
Definition of format masks for datetime elements can
be found in the SQL Reference manual on tahiti.oracle.com,
specifically:
http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/sql_elements004.h
tm#i34924