Format date and time in a Windows batch script

Question

I ended up with this script:

set hour=%time:~0,2%
if "%hour:~0,1%" == " " set hour=0%hour:~1,1%
echo hour=%hour%
set min=%time:~3,2%
if "%min:~0,1%" == " " set min=0%min:~1,1%
echo min=%min%
set secs=%time:~6,2%
if "%secs:~0,1%" == " " set secs=0%secs:~1,1%
echo secs=%secs%

set year=%date:~-4%
echo year=%year%

:: On WIN2008R2 e.g. I needed to make your 'set month=%date:~3,2%' like below ::otherwise 00 appears for MONTH

set month=%date:~4,2%
if "%month:~0,1%" == " " set month=0%month:~1,1%
echo month=%month%
set day=%date:~0,2%
if "%day:~0,1%" == " " set day=0%day:~1,1%
echo day=%day%

set datetimef=%year%%month%%day%_%hour%%min%%secs%

echo datetimef=%datetimef%

Here is how I generate a log filename (based on http://ss64.com/nt/syntax-getdate.html):

@ECHO OFF
:: Check WMIC is available
WMIC.EXE Alias /? >NUL 2>&1 || GOTO s_error

:: Use WMIC to retrieve date and time
FOR /F "skip=1 tokens=1-6" %%G IN ('WMIC Path Win32_LocalTime Get Day^,Hour^,Minute^,Month^,Second^,Year /Format:table') DO (
   IF "%%~L"=="" goto s_done
      Set _yyyy=%%L
      Set _mm=00%%J
      Set _dd=00%%G
      Set _hour=00%%H
      SET _minute=00%%I
      SET _second=00%%K
)
:s_done

:: Pad digits with leading zeros
      Set _mm=%_mm:~-2%
      Set _dd=%_dd:~-2%
      Set _hour=%_hour:~-2%
      Set _minute=%_minute:~-2%
      Set _second=%_second:~-2%

Set logtimestamp=%_yyyy%-%_mm%-%_dd%_%_hour%_%_minute%_%_second%
goto make_dump

:s_error
echo WMIC is not available, using default log filename
Set logtimestamp=_

:make_dump
set FILENAME=database_dump_%logtimestamp%.sql
...

@ECHO OFF
: Sets the proper date and time stamp with 24Hr Time for log file naming
: convention ('YYYYMMDD_HHMMSS')

: Scrapes the characters out of their expected permissions in the date/time
: environment variables.

: Expects a date format of '____MM_DD_YYYY'
: Expects a time format of 'HH:MM:SS' or ' H:MM:SS'

SET HOUR=%time:~0,2%
SET dtStamp9=%date:~-4%%date:~4,2%%date:~7,2%_0%time:~1,1%%time:~3,2%%time:~6,2% 
SET dtStamp24=%date:~-4%%date:~4,2%%date:~7,2%_%time:~0,2%%time:~3,2%%time:~6,2%

if "%HOUR:~0,1%" == " " (SET dtStamp=%dtStamp9%) else (SET dtStamp=%dtStamp24%)

ECHO %dtStamp%

PAUSE

I usually do it this way whenever I need a date/time string:

set dt=%DATE:~6,4%_%DATE:~3,2%_%DATE:~0,2%__%TIME:~0,2%_%TIME:~3,2%_%TIME:~6,2%
set dt=%dt: =0%

This is for the German date/time format (dd.mm.yyyy hh:mm:ss). Basically I concatenate the substrings and finally replace all spaces with zeros.

The resulting string has the format: yyyy_mm_dd__hh_mm_ss

---

Short explanation of how substrings work:

%VARIABLE:~num_chars_to_skip,num_chars_to_keep%

So to get just the year from a date like "29.03.2018" use:

%DATE:~6,4%
       ^-----skip 6 characters
         ^---keep 4 characters 

If PowerShell is installed, then you can easily and reliably get the Date/Time in any format you'd like, for example:

for /f %%a in ('powershell -Command "Get-Date -format yyyy_MM_dd__HH_mm_ss"') do set datetime=%%a
move "%oldfile%" "backup-%datetime%"

Of course nowadays PowerShell is always installed, but on Windows XP you'll probably only want to use this technique if your batch script is being used in a known environment where you know PS is available (or check in your batch file if PowerShell is available...)

You may reasonably ask: why use a batch file at all if you can use PowerShell to get the date/time, but I think some obvious reasons are: (a) you're not all that familiar with PowerShell and still prefer to do most things the old-fashioned way with batch files or (b) you're updating an old script and don't want to port the whole thing to PS.

I came across this problem today and solved it with:

SET LOGTIME=%TIME: =0%

It replaces spaces with 0s and basically zero-pads the hour.

After some quick searching I didn't find out if it required command extensions (still worked with SETLOCAL DISABLEEXTENSIONS).