Powershell Subtract 1 Day from Variable Date

Single line conversion and subtraction.

(Get-Date $date).AddDays(-1)

This thread really helped me a lot and here's what I was trying to do. Sharing so others can see more things you can do with Get-Date and AddDays.

PS C:\Users\zzz> (Get-Date $date).AddDays(0).ToString("MMddyyyy")
07162019

PS C:\Users\zzz> (Get-Date $date).AddDays(-1).ToString("MMddyyyy")
07152019

Expanding on Mani Live's answer ... to use in a regular batch file:

for /F "usebackq" %%d in (`powershell -STA -ExecutionPolicy ByPass -command "echo ((Get-Date).AddDays(-10)).ToString(\"yyyy-MM-dd\")"`) do set ten_days_ago=%%d

Your variable is String. run $date.gettype() it will output string.

$date = "2016-09-08"
$date.gettype()
IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     String                                   System.Object

to be able to use datetime functions you need a datetime variable.

$date = get-date("2016-09-08")
$date.gettype()
  IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Datetime                                   System.Object
$date.adddays(-1)
Wednesday, September 7, 2016 12:00:00 AM

then you can start using formatting of your choice.

You can also cast the string to a datetime:

$date = [datetime]"2016-09-08"

Or assign the string to a strictly-typed datetime variable:

[datetime]$date = "2016-09-08"