How to Change Global Light in Photoshop CC (per Document and Global)
Global Light in Photoshop affects couple of Layer Effects: Bevel and Emboss, Inner Shadow and Drop Shadow. When Use Global Light option is checked, changing Global Light for any of mentioned effects will change light automatically for remaining two. This is change per document and can be done from Layer Style dialog, using right/Cmd + click on Effects below layer thumb > Global Light or from Layer > Layer Style > Global Light.
As mentioned change to Global Light with document open won't change default values: Angle 120 and Altitude 30. To make global change for every new document you must close all open documents and to visit Layer > Layer Style > Global Light dialog. Type values in Angle and Altitude text fields and confirm on OK button.
Note: changes to Global Light on global basis (without any document open) won't change Global Light when you open already saved documents, it will affect only new documents including Layer Styles/Effects copied and pasted from other documents. And last info: typed values will remain defaults until you change them manually or until you reset Photoshop CC preferences.
Product used in this tip:
Adobe Photoshop CC
Photoshop / Layer effects and styles