计算两个字符串日期相差的天数

我们有两个字符串 20130728　　和　　20130803　　如何利用计算相差的天数呢

time1=time.strptime("20130803","%Y%m%d")

time2=time.strptime("20130728","%Y%m%d")

time1和time2　　如下 结构

time.struct_time(tm_year=2013, tm_mon=8, tm_mday=03, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=4, tm_yday=242, tm_isdst=-1)

于是乎，diffday=365*(time1.tm_year-time2.tm_year) + time.tm_mday-time2.tm_mday