converts a PowerShell/.NET DateTime to a unix timestamp (Milliseconds since 1 Jan, 1970) Useful for creating JSON that can be understood by the .NET JavaScriptSerializer

unix-timestamp.ps1

function ConvertTo-UnixTimestamp {
	$epoch = Get-Date -Year 1970 -Month 1 -Day 1 -Hour 0 -Minute 0 -Second 0	
 	$input | % {		
		$milliSeconds = [math]::truncate($_.ToUniversalTime().Subtract($epoch).TotalMilliSeconds)
		Write-Output $milliSeconds
	}	
}

Get-Date | ConvertTo-UnixTimestamp

Hopefully PS3 will make this redundant

Ancient gist but as I stumbled to this from google, I will leave comment. Even in version 2 there is available Get-Date -UFormat %s, which return unix timestamp with five decimals, so multiplying it will do the trick. Note: it will return System.String, not System.DateTime