Real injection timing.
Mechanical or ECM.

Mechanical pumps get timed by feel and a dial indicator. Many ECMs never report injection timing at all, and the ones that do only show what's commanded, not what the injector actually does. TimingBuddy measures the real injection event externally, against crankshaft position, right on the running engine. Degrees BTDC, resolved to a tenth, live on your phone. The job of a diesel injection timing meter, no shop bench required.