@echo off
set/p "data=Please enter a date (MM/DD):"
set "error=echo,Invalid date&pause&goto :eof"
setlocal enabledelayedexpansion
for /l %%i in (5,-1,0) do (
    set "data%%i=!data:~%%i,1!"
    if not "!data%%i!"=="" (
        if %%i equ 5 (
            %error%
        ) else if %%i equ 2 (
            if "!data%%i!" neq "/" %error%
        ) else if "!data%%i!" lss "0" (
            %error%
        ) else if "!data%%i!" gtr "9" %error%
    ) else (
        if %%i equ 4 %error%
    )
)
if %data0% equ 0 set "data0="
if %data3% equ 0 set "data3="
set mm=%data0%%data1%
set dd=%data3%%data4%
if %mm% gtr 12 %error%
if %dd% gtr 31 %error%
for /f "tokens=2" %%i in ('wmic os get codeset^,localdatetime') do (
    set yyyy=%%i
    set "yyyy=!yyyy:~0,4!"
    )
endlocal&set /a mm=%mm%,dd=%dd%,yyyy=%yyyy%
set /a "gtm=!(mm-4)|!(mm-6)|!(mm-9)|!(mm-11)","leap=!(yyyy%%4)&!!(yyyy%%100)|!(yyyy%%400)","dlim=!(mm-2)*(28+leap)+gtm*30+(!!(mm-2)&!gtm)*31"
if %dd% gtr %dlim% (%error%) else (echo,Valid date)
pause&exit /bCOPY

if not "%md:~2,1%"=="/" goto :pCOPY

@echo off
set /p str=input:
setlocal enabledelayedexpansion
>1.txt echo=#!str!
endlocal
findstr /rxc:"#[0-9][0-9]/[0-9][0-9]" 1.txt
if not errorlevel 1 (
	echo ok
)
pauseCOPY

findstr /x "0[1-9]/[0-2][1-9] 1[0-2]/[0-2][1-9] 0[1-9]/[12]0 1[0-2]/[12]0 0[13-9]/30 1[0-2]/30 0[13578]/31 1[02]/31"COPY

再练一把 ‘纯P进行到底’ 的脑力操...
给一个纯P版本的日期输入合法性检查代码，不用外部方法，不用正则匹配
算法简明得益于采用 ‘字典变量’，尽可能考虑了各种防错对策》分隔符及其错位，日月数值溢出，日月相关，平闰年天数区分... 还是回归日月均为两位数的要求。
以下代码采用循环输入以便完成各种测试，直至空回车退出...

@echo off &setlocal
set/a "_1=31,_2=28,_3=31,_4=30,_5=31,_6=30,_7=31,_8=31,_9=30,_10=31,_11=30,_12=31,y=%date:~,4%%%4"
if %y% equ 0 set "_2=29"
:[md_loop]
set "md=" &set "c=" &set/p "md=输入日期（月值/日值）："
if not defined md endlocal&exit/b
setlocal enabledelayedexpansion &set k=!md:"=!
if "!k!" neq "!md!" echo,非法&endlocal&goto[md_loop]
endlocal &if "%md:~5%" neq "" echo,非法&goto[md_loop]
if "%md:~4,1%"=="" echo,非法&goto[md_loop]
for /f "tokens=1,2 delims=/" %%1 in ("%md%") do set "m=%%1"&set "d=%%2"
if "%md%"=="%m%" echo,非法&goto[md_loop]
for /f "delims=0123456789" %%n in ("%m%%d%") do set "c=1"
if defined c echo,非法&goto[md_loop]
if not defined d echo,非法&goto[md_loop]
if "%md:~2,1%" neq "/" echo,非法&goto[md_loop]
if "%m:~0,1%" equ "0" if "%m:~1,1%" neq "" set "m=%m:~1%"
set "_m=_%m%" &set "w=非法" &setlocal enabledelayedexpansion
if "%d:~0,1%" equ "0" if "%d:~1,1%" neq "" set "d=%d:~1%"
if %d% gtr 0 if %d% leq !%_m%! set "w=合法"
echo,!w!&endlocal&goto[md_loop]COPY