$VIServers = @(
    "server1",
    "server2",
    "server3"
)

Connect-VIServer $VIServers

$vmName = "VMname"
$snapTime = Get-Date "22/06/18 21:00"
$snapName = "taskname"
$snapDescription = 'Scheduled snapshot'
$snapMemory = $true
$snapQuiesce = $false
$emailAddr = 'email@me.nl'

$vm = Get-VM $vmName

foreach ($VIServer in $VIServers) {
    if ($vm.Uid -like "*$VIServer*") {
        $SIServer = $VIServer
    }
}

$si = Get-View ServiceInstance -Server $SIServer
$scheduledTaskManager = Get-View $si.Content.ScheduledTaskManager -Server $SIServer

$spec = New-Object VMware.Vim.ScheduledTaskSpec
$spec.Name = "Snapshot",$vm.Name -join ' '
$spec.Description = $_.Description
$spec.Enabled = $true
$spec.Notification = $emailAddr
$spec.Scheduler = New-Object VMware.Vim.OnceTaskScheduler
$spec.Scheduler.runat = $snapTime
$spec.Action = New-Object VMware.Vim.MethodAction
$spec.Action.Name = "CreateSnapshot_Task"
@($snapName,$snapDescription,$snapMemory,$snapQuiesce) | %{
    $arg = New-Object VMware.Vim.MethodActionArgument
    $arg.Value = $_
    $spec.Action.Argument += $arg
}
$scheduledTaskManager.CreateObjectScheduledTask($vm.ExtensionData.MoRef, $spec)