Today I needed to get the system boot time of my computer.
You can either open the system log and look for the entries a Windows start up writes there, or you can let a tool do the work:
@echo off systeminfo | find "System Boot Time" pause
In my case the result looks like this:
System Boot Time: 13.10.2016, 09:14:50 Press any key to continue . . .
There are a lot more options, detailed in this answer on StackOverflow.