有时备份文件时，需要重命名名字，加上日期和时间。
比如：
把 c:\aaa
目录备份到
c:\aaaSave\aaa_20181106_122020
命令：
md c:\aaaSave\aaa_%date:~,4%%date:~5,2%%date:~8,2%_%time:~0,2%%time:~3,2%%time:~6,2% xcopy c:\aaa\* c:\aaaSave\aaa_%date:~,4%%date:~5,2%%date:~8,2%_%time:~0,2%%time:~3,2%%time:~6,2%