#两个日期相隔多少天，例：2008-10-03和2008-10-01是相隔两天 
def datediff(beginDate,endDate): 
    format="%Y-%m-%d"; 
    bd=strtodatetime(beginDate,format) 
    ed=strtodatetime(endDate,format)     
    oneday=datetime.timedelta(days=1) 
    count=0
    while bd!=ed: 
        ed=ed-oneday 
        count+=1
    return count