DateTime to ISO8601UTC
$date.ToUniversalTime().ToString("yyyy-MM-ddTHH:mm:ss.fffZ")
Convert From Unix Time
[timezone]::CurrentTimeZone.ToLocalTime(([datetime]'1/1/1970').AddSeconds($UnixTime))
Convert To Unix Time
[int][double]::Parse((Get-Date ($date).touniversaltime() -UFormat %s))
End of Month
(Get-Date $date.Date -day 1).AddMonths(1).AddMilliseconds(-1)