@echo off
rem 假设系统日期格式为：2009-06-14 星期日
set day=1%date:~5,2%
set /a day%%=100
copy /y "C:\test\a.txt" "C:\test\%day%"

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探讨

BatchFile code
@echo off
rem 假设系统日期格式为：2009-06-14 星期日
set day=1%date:~5,2%
set /a day%%=100
copy /y "C:\test\a.txt" "C:\test\%day%"




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time /t

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rem for DOS/NT
echo exit|%comspec% /k prompt $T$_ | find ":" > time.txt

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@echo on
rem  supoose the current date is 2009-6-15
rem  this bat file will make a file at c:\ as 15 and copy the c:\file into  file
ren if you don't want to get out the command you can change the code as @echo off
date /t
set day=1%date:~9,2%  
@echo make file as date time .for example  15
md  c:\%day%
echo the "c:\files " means what file you want to copy to the datetime file
echo copy /y  "c:\file"   "c:\%day%"

------解决方案--------------------
date
time/t