Hi, I am working on hotel management module in odoo version 8.

I wish to calculate number of nights stayed between check-in date and check-out date.  

Can anyone help me with this? How to calculate this?

I tried calculating it as per the number of days but not worked for me.

Here is my code,

Defined one class for Hotel Reservation,

class hotel_reservation(osv.Model):

_name = "hotel.reservation"

_rec_name = "reservation_no"

_description = "Reservation"

_order = 'reservation_no desc'

_columns = {

'reservation_no': fields.char('Reservation No', size=64, required=True, readonly=True),

'date_order':fields.datetime('Date Ordered', required=True, readonly=True, states={'draft':[('readonly', False)]}),

'warehouse_id':fields.many2one('stock.warehouse', 'Hotel', readonly=True, required=True, states={'draft':[('readonly', False)]}),

'partner_id':fields.many2one('res.partner', 'Guest Name', readonly=True, required=True, states={'draft':[('readonly', False)]}),

'pricelist_id':fields.many2one('product.pricelist', 'Price List', required=True, readonly=True, states={'draft':[('readonly', False)]}, help="Pricelist for current reservation. "),

'partner_invoice_id':fields.many2one('res.partner', 'Invoice Address', readonly=True, states={'draft':[('readonly', False)]}, help="Invoice address for current reservation. "),

'partner_order_id':fields.many2one('res.partner', 'Ordering Contact', readonly=True, states={'draft':[('readonly', False)]}, help="The name and address of the contact that requested the order or quotation."),

'partner_shipping_id':fields.many2one('res.partner', 'Delivery Address', readonly=True, states={'draft':[('readonly', False)]}, help="Delivery address for current reservation. "),

'checkin': fields.datetime('Expected-Date-Arrival', required=True, readonly=True, states={'draft':[('readonly', False)]}),

'checkout': fields.datetime('Expected-Date-Departure', required=True, readonly=True, states={'draft':[('readonly', False)]}),

'adults':fields.integer('Adults', size=64, readonly=True, states={'draft':[('readonly', False)]}, help='List of adults there in guest list. '),

'children':fields.integer('Children', size=64, readonly=True, states={'draft':[('readonly', False)]}, help='Number of children there in guest list. '),

'reservation_line':fields.one2many('hotel_reservation.line', 'line_id', 'Reservation Line', help='Hotel room reservation details. '),

'state': fields.selection([('draft', 'Draft'), ('confirm', 'Confirm'), ('cancel', 'Cancel'), ('done', 'Done')], 'State', readonly=True),

'folio_id': fields.many2many('hotel.folio', 'hotel_folio_reservation_rel', 'order_id', 'invoice_id', 'Folio'),

'dummy': fields.datetime('Dummy'),

  }

    _defaults = {

        'reservation_no': lambda obj, cr, uid, context: obj.pool.get('ir.sequence').get(cr, uid, 'hotel.reservation'),

        'state': lambda *a: 'draft',

        'date_order': lambda *a: time.strftime('%Y-%m-%d %H:%M:%S'),

    }

Also, 2 on change methods,

def on_change_checkin(self, cr, uid, ids, date_order, checkin_date=time.strftime('%Y-%m-%d %H:%M:%S'), context=None):

if date_order and checkin_date:

if checkin_date < date_order:

raise osv.except_osv(_('Warning'), _('Checkin date should be greater than the current date.'))

return {'value':{}}

def on_change_checkout(self, cr, uid, ids, checkin_date=time.strftime('%Y-%m-%d %H:%M:%S'), checkout_date=time.strftime('%Y-%m-%d %H:%M:%S'), context=None):

if not (checkout_date and checkin_date):

return {'value':{}}

if checkout_date < checkin_date:

raise osv.except_osv(_('Warning'), _('Checkout date should be greater than the Checkin date.'))

delta = datetime.timedelta(days=1)

addDays = datetime.datetime(*time.strptime(checkout_date, '%Y-%m-%d %H:%M:%S')[:5]) + delta

val = {'value':{'dummy':addDays.strftime('%Y-%m-%d %H:%M:%S')}}

return val