How do I find the install time and date of Windows?

Question

This might sound like a little bit of a crazy question, but how can I find out (hopefully via an API/registry key) the install time and date of Windows?

The best I c

Answer 1

Windows 10 OS has yet another registry subkey, this one in the SYSTEM hive file:

Computer\HKEY_LOCAL_MACHINE\SYSTEM\Setup\

The Install Date information here is the original computer OS install date/time. It also tells you when the update started, ie

 Computer\HKEY_LOCAL_MACHINE\SYSTEM\Setup\Source OS (Updated on xxxxxx)."

This may of course not be when the update ends, the user may choose to turn off instead of rebooting when prompted, etc...

The update can actually complete on a different day, and

Computer\HKEY_LOCAL_MACHINE\SYSTEM\Setup\Source OS (Updated on xxxxxx)"

will reflect the date/time it started the update.