Recently when troubleshooting some Maintenance Window issues for SCCM 2012 clients, I was watching the client log ServiceWindowManager.log

Each Maintenance Window has a type. For example I set a Maintenance Window for All Deployments.

You can see that this had Type=1.

If you are curious to see what other maintenance windows you may have set for the client, you can check out this link or look at the table below.

https://msdn.microsoft.com/en-us/library/jj155420.aspx

Value	Service Window Type	Description
1	ALLPROGRAM_SERVICEWINDOW	All Programs Service Window
2	PROGRAM_SERVICEWINDOW	Program Service Window
3	REBOOTREQUIRED_SERVICEWINDOW	Reboot Required Service Window
4	SOFTWAREUPDATE_SERVICEWINDOW	Software Update Service Window
5	OSD_SERVICEWINDOW	OSD Service Window
6	USER_DEFINED_SERVICE_WINDOW	Corresponds to non-working hours.