Full Idea
Roughly speaking, we use calendars to track the order of events in time, and clocks to track changes and the passing of events.
Gist of Idea
We use calendars for the order of events, and clocks for their passing
Source
Adrian Bardon (Brief History of the Philosophy of Time [2013], Intro)
Book Reference
Bardon,Adrian: 'Brief History of the Philosophy of Time' [OUP 2013], p.1
A Reaction
So calendars cover the B-Series and clocks the A-Series, showing that this distinction is deeply embedded, and wasn't invented by McTaggart.