Full Idea
McTaggart argued that time involves change, only the A-series can explain change, the A-series involves contradictions (past, present and future), and hence time is unreal.
Clarification
A-series time is a fixed background to events
Gist of Idea
Time involves change, only the A-series explains change, but it involves contradictions, so time is unreal
Source
report of J.M.E. McTaggart (The Nature of Existence vol.2 [1927]) by E.J. Lowe - A Survey of Metaphysics p.313
Book Reference
Lowe,E.J.: 'A Survey of Metaphysics' [OUP 2002], p.313
A Reaction
I doubt whether it is a logical contradiction to say Waterloo has been past, present and future, though it is odd.