Don't mention "manual" in the Automation Tools communities
Try like this
$vms=Get-VM
$start= (Get-Date).AddDays(-1)
$snapTaken=Get-VIEventPlus-Entity$vms-EventType"TaskEvent"-Start$start|
where {$_.Info.DescriptionId-eq"VirtualMachine.createSnapshot"}
$snapRevert=Get-VIEventPlus-Entity$vms-EventType"com.vmware.vc.vm.VmStateRevertedToSnapshot"-Start$start
It should produce 2 arrays, one holding the snapshots that were taken and the snapshot reverts