Right, A-theory's origin has to be 'the present moment'. I think A theory probably even excludes the possibility of a beginning of time (Hawking once wrote an article in which he had to coin the phrase 'imaginary time' to discuss the question of how long ago the big bang was). I'm sure that's not an uncontroversial claim though.

This may seem like a kind of fringe metaphysical concern (and it's certainly a metaphysical concern), but I think the question of the reality of change is probably the original philosophical problem.