Writing a batch file with PowerShell

You could run the PowerShell command line as follows to get the value in a variable in your batch script:

@echo off

for /f "tokens=* delims=" %%d in (
  'powershell.exe -Command "(Get-Date).AddDays(-1).ToString(\"yyyyMMdd\")"'
) do set "yesterday=%%d"

move *%yesterday%*.xml D:\Sample\

You shouldn't name the variable %date%, because that is a variable CMD automatically populates with the current date. See help set:

%DATE% - expands to current date using same format as DATE command.

However, as @alroc suggested in the comments to your question, it would probably be simpler to just write the entire script in PowerShell:

$yesterday = (Get-Date).AddDays(-1).ToString('yyyyMMdd')
Move-Item "*$yesterday*.xml" 'D:\Sample'

If I understand your question correctly, you want to write a Batch Script (.bat) that uses Powershell to get the previous Date.

Below is what you can put in your .bat Script to get the value.

powershell -Command (Get-Date).AddDays(-1).ToString('yyyyMMdd')

You do not need to "pass back" the variable. Instead, you just make the output of the powershell call the information you want. Using your code you posted, there is no output. Using what is above, however, will be equivalent to "returning" the $date variable in your code.

Batch doesn't really have a simple way to capture the variable, however. There are two main ways to capture variables. You either use a for loop (this is kind of a hack), or to write the output to a file, then read that file into a variable.

Method 1 - For Loop
Here is the code to capture the output into variable named v (access with %v%).

for /f %d in (
  'powershell.exe -Command "(Get-Date).AddDays(-1).ToString(\"yyyyMMdd\")"'
) do set "v=%d"

Method 2 - File Output
Here, we write the powershell output to a file, whose name is stored in the variable tempFile. Then, we read the file's content back into the variable named v. Finally, we delete the tempFile.

powershell.exe -Command (Get-Date).AddDays(-1).ToString('yyyyMMdd') > %tempFile%
set /p v=< %tempFile%
del %tempFile%

You could as well do it in CMD.exe completly, although it is a little bit more complex...

:Get_Dates
set day=%DATE:~-10,2%
set month=%DATE:~-7,2%
set year=%DATE:~-4%

set TODAY=%year%-%month%-%day%

set /a tag-=1
if %day% LEQ 0 set /a monat-=1
if %month% LEQ 0 set /a jahr-=1 & set monat=12

if %day% GEQ 1 goto :done
rem day is in the previous month
if %month% EQU 1 set tag=31
if %month% EQU 3 set tag=31
if %month% EQU 4 set tag=30
if %month% EQU 5 set tag=31
if %month% EQU 6 set tag=30
if %month% EQU 7 set tag=31
if %month% EQU 8 set tag=31
if %month% EQU 9 set tag=30
if %month% EQU 10 set tag=31
if %month% EQU 11 set tag=30
if %month% EQU 12 set tag=31

if %month% NEQ 2 goto :done
rem februar so check year
set /a mod4=year % 4
set /a mod100=year % 100
set /a mod400=year % 400
set day=28
if %mod4% NEQ 0 goto :done
set day=29
if %mod100% NEQ 0 goto :done
set day=28
if %mod400% NEQ 0 goto :done
set day=29

:done