python 对时间操作

from datetime import datetime,timedelta      

'date_test':fields.function(_datetime_all,type='datetime',  string=u'测试'),

函数：形式

def _datetime_all(self, cr, uid, ids, field_name, arg, context=None):

        res = {}

        for order in self.browse(cr, uid, ids, context=context):

            aa = order.lreport_date

            dt = datetime.strptime(aa, "%Y-%m-%d %H:%M:%S")

            d = dt-timedelta(hours=8)

            order.date_test=d

            va= order.date_test

            res[order.id] = va

        return  res

这个是on_change事件：

def on_change_time(self,cr,uid,ids,date,context=None):

        result={}

        if date:

            dt = datetime.strptime(date, "%Y-%m-%d %H:%M:%S")

            d = dt-timedelta(hours=8)

            result['date_test']=d

        return {'value':result}

 <field name="lreport_date"  on_change="on_change_time(lreport_date)"/>

 on_change="on_change_time(date)"