Hi,

try :

from datetime import datetime, timedelta

from dateutil.relativedelta import relativedelta

cr.execute("""select rp.name, cl.name,cl.date_open,cl.state,
he.lead_target, 
count(cl.user_id) as achieved,
round(((cast(count(cl.user_id) as decimal(2))/he.lead_target)*100)) as val
from crm_lead cl, 
hr_employee he, 
res_users rs, 
res_partner rp
where cl.type='opportunity' and  
rs.id=he.user_id and 
he.user_id=cl.user_id and
rp.id=rs.partner_id and 
create_date>='2013-04-28' and create_date<=%s
""", (str(datetime.now().strftime('%Y-%m-%d %H:%M:%S.%f') + relativedelta(days=15).strftime('%Y-%m-%d %H:%M:%S.%f')),))

Bye