Full Idea
McTaggart says we can speak of events in time in two ways, as past, present or future, or as being before or after or simultaneous with one another. The first cannot be reduced to the second, as the second makes no provision for the passage of time.
Gist of Idea
For McTaggart time is seen either as fixed, or as relative to events
Source
report of J.M.E. McTaggart (The Nature of Existence vol.2 [1927], II.329-) by A.J. Ayer - The Central Questions of Philosophy 1.D
Book Reference
Ayer,A.J.: 'The Central Questions of Philosophy' [Penguin 1976], p.15