$date.ToUniversalTime().ToString("yyyy-MM-ddTHH:mm:ss.fffZ")
Format a DateTime value in the ISO8601UTC format
PS C:\> $Date = Get-Date >> $date.ToUniversalTime().ToString("yyyy-MM-ddTHH:mm:ss.fffZ") 2019-03-28T16:06:00.050Z
$date.ToUniversalTime().ToString("yyyy-MM-ddTHH:mm:ss.fffZ")
DetailsPS C:\> $Date = Get-Date >> $date.ToUniversalTime().ToString("yyyy-MM-ddTHH:mm:ss.fffZ") 2019-03-28T16:06:00.050Z