Well, no - it can't use AC directly as an input, as AC implies that the signal goes above and below the 0v reference; the negative voltage would burn up the 555 timer.
It might use rippled DC input, as long as the rippled DC did not exceed the limits of the timers' power supply rails.
Rippled DC can resemble AC (as a sine wave), but isn't centered around the 0v reference.
Good point, wookie. I missed that. Or did I assume ht knew that? It's so hard to guess the intellectual level of a person when you've only seen him make one sentence.