Formatting Date and Time in Windows Batch Scripts

Introduction

In many automation tasks, you may need to generate files with unique names based on the current date and time. This can help avoid overwriting existing files or organizing logs more effectively. In Windows batch scripts, formatting date and time correctly requires manipulating system environment variables such as %DATE% and %TIME%. This tutorial will guide you through various methods to format date and time in a way that is suitable for filenames or other purposes.

Understanding Date and Time Environment Variables

In Windows, the %DATE% and %TIME% environment variables provide access to the current system date and time. However, their formats vary depending on your system’s locale settings:

• Date Format: Typically MM/DD/YYYY in the US or DD.MM.YYYY in many European countries.
• Time Format: Generally HH:MM:SS, with hours ranging from 0 to 23.

These variables can be sliced into specific components using substring operations, allowing you to rearrange and format them as needed.

Basic Substring Extraction

The syntax for extracting substrings in batch scripting is:

%VARIABLE:~start,length%

• start: The zero-based position where the extraction begins.
• length: The number of characters to extract.

For instance, if you have a date variable %DATE% with value 28/07/2009, extracting the year can be done as follows:

set year=%date:~-4%

This command extracts the last four digits from %date%, giving us 2009.

Formatting Date and Time

Here are several methods to format date and time in a batch script.

Method 1: Using Substring Operations

You can extract components directly using substring operations. This method works well if you know your system’s locale:

set year=%date:~-4%
set month=%date:~4,2%
if "%month:~0,1%" == " " set month=0%month:~1,1%

set day=%date:~7,2%
if "%day:~0,1%" == " " set day=0%day:~1,1%

set hour=%time:~0,2%
if "%hour:~0,1%" == " " set hour=0%hour:~1,1%

set minute=%time:~3,2%
if "%minute:~0,1%" == " " set minute=0%minute:~1,1%

set second=%time:~6,2%
if "%second:~0,1%" == " " set second=0%second:~1,1%

set datetimef=%year%%month%%day%_%hour%%minute%%second%
echo %datetimef%

This approach ensures that all components are correctly padded with leading zeros when necessary.

Method 2: Using WMIC

For a more robust solution that is less dependent on locale settings, you can use WMIC (Windows Management Instrumentation Command-line):

@ECHO OFF

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%
echo %logtimestamp%

This method queries the system for accurate date and time components, ensuring consistent results across different locales.

Method 3: Using PowerShell

If PowerShell is available on your system (common in modern Windows environments), you can achieve reliable formatting:

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

This method leverages PowerShell’s Get-Date cmdlet, which provides precise control over date and time formatting.

Conclusion

Formatting the current date and time in a Windows batch script can be achieved through several methods, each with its own advantages. Substring operations work well for straightforward cases but depend on locale settings. WMIC offers a more robust solution by querying system information directly, while PowerShell provides a modern approach if available. Choose the method that best suits your needs based on your environment and familiarity with these tools.