Boot Log
System.log
In this location you will be able to view the boot up time for your computer. It is contained in the system log. The time stamp is stored as Unix Epoch time and you can use a site such as https://www.epochconverter.com/ to easily convert the time stamp to human time.
Copy and Paste this into the terminal to open the log with the console application.
open /private/var/log/system.log
Now you can search using Command + F for “BOOT_TIME”.