Just a quick one-liner that I had to use today. Gets all AD Users created in the past 7 days:

Get-ADUser -Filter "created -gt '$((Get-Date).AddDays(-7).ToShortDateString())'"

I had to tack on the .ToShortDateString() method, as the filter doesn’t like the long-formatted date and brings back all sorts of accounts, not just those from the past 7 days.