Fwd: Timestamp Query Parameters

I'm just starting out with psycopg2. I'm trying to pass a timestamp query parameter to an sql query. Unfortunately the constructed query returns nothing, even though it should. The code follows; does anyone see what I'm doing wrong?

date = datetime.now().strftime("%Y-%m-%d")
params = [datetime.strptime(date + " 00:00:00", '%Y-%m-%d %H:%M:%S'), datetime.s
trptime(date + " 23:59:59", '%Y-%m-%d %H:%M:%S')]
print params
try:
  query = """select * from timesheet
s where submitted=true and started_at between '%s' and '%s'"""
  cursor.mogrify(query, params)