Testing for End of Month in PowerShell

This is one of those blog posts you write so that 2 years later, you can look it up to remind yourself how to do something.

I found myself needing to figure out if “today” was the end of the month in PowerShell. In T-SQL, this is easy, as we have the EOMONTH() function. But PowerShell (the .NET System.DateTime struct) doesn’t have the same thing.

Fortunately, the lack of a .NET EOMONTH() function is easily remedied with the DaysInMonth() method. I just need to check the day of month against the number of days in the month.

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$CurrentDate = Get-Date;
$IsEndOfMonth = $CurrentDate.Day -eq [System.DateTime]::DaysInMonth($CurrentDate.Year,$CurrentDate.Month) ? $true : $false;

This will work for any date by passing (for example) -Date 1955-11-05 to Get-Date.

In the past, I haven’t been a big fan of ternary operators but they’re growing on me, especially for quick hits like this.

Important note for formatting here - the spaces around the : operator are mandatory. If you use a formatter, it will probably not correct this because there are cases where <string>:<string> is valid (like $Using:variablename or -Verbose:$VerbosePreference). Your editor (assuming it understands PowerShell, like VSCode) will flag the lack of spaces as an error here because it’s not valid in this context. My recommendation: just get in the habit of putting spaces around both the ? and :.