How do I get the day month and year from a Windows cmd.exe script?

To get the year, month, and day you can use the %date% environment variable and the :~ operator. %date% expands to something like Thu 08/12/2010 and :~ allows you to pick up specific characters out of a variable:

set year=%date:~10,4%
set month=%date:~4,2%
set day=%date:~7,2%
set filename=%year%_%month%_%day%

Use %time% in similar fashion to get what you need from the current time.

set /? will give you more information on using special operators with variables.

The following batch code returns the components of the current date in a locale-independent manner and stores day, month and year in the variables CurrDay, CurrMonth and CurrYear, respectively:

for /F "skip=1 delims=" %%F in ('
    wmic PATH Win32_LocalTime GET Day^,Month^,Year /FORMAT:TABLE
') do (
    for /F "tokens=1-3" %%L in ("%%F") do (
        set CurrDay=0%%L
        set CurrMonth=0%%M
        set CurrYear=%%N
    )
)
set CurrDay=%CurrDay:~-2%
set CurrMonth=%CurrMonth:~-2%
echo Current day  :  %CurrDay%
echo Current month:  %CurrMonth%
echo Current year :%CurrYear%

There are two nested for /F loops to work around an issue with the wmic command, whose output is in unicode format; using a single loop results in additional carriage-return characters which impacts proper variable expansion.

Since day and month may also consist of a single digit only, I prepended a leading zero 0 in the loop construct. Afterwards, the values are trimmed to always consist of two digits.