 McTaggart begins his argument by distinguishing two ways in which positions in time can be ordered. First, he says, positions in time can be ordered according to their possession of properties like being two days future, being one day future, being present, being one day past, etc. These properties are often referred to now as “A properties” because McTaggart calls the series of times ordered by these properties “the A series”. But he says that positions in time can also be ordered by two-place relations like two days earlier than, one day earlier than, simultaneous with, etc. These relations are now often called “B relations” because McTaggart calls the series of times ordered by these relations “the B series”.