Xiaogang and his mother went on a trip. They set off at 7:00 pm on October 1st and arrived home at 3:00 pm on October 2nd. How long did they spend together?
小刚和妈妈去旅游，10月1日晚上7：00出发，10月2日下午3：00到家，他们共在外多长时间？
<result>20</result>