PS H:> (New-TimeSpan -Start $date1 -End $date2).TotalSeconds
1289923177.87462
New-TimeSpan can be used to do that. For example,
$date1 = Get-Date -Date "01/01/1970"
$date2 = Get-Date
(New-TimeSpan -Start $date1 -End $date2).TotalSeconds
Or just use this one line command
(New-TimeSpan -Start (Get-Date "01/01/1970") -End (Get-Date)).TotalSeconds
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