I saw this post the other day but it wasn't quite what I was looking for: LDMS query filtering on specific time during the current day. I wanted to create a report of any machines which recently rebooted. The one caveat was that machines don't send update inventory data after a reboot, so this value isn't as accurate as I like but I found a way to do it, with the help of a colleague.
Here is how you can query uptime by the minute. I went with 180 minutes, which worked well enough to get some hits: "Computer"."OS"."Last Startup Time" > DATEADD(mi, -180, GETDATE())
Hope this helps anyone else looking to do the same.