If no revised date is mentioned in the paper, does this means the paper is directly accepted by the journal? When I am reading papers, sometimes I see statements like 


  Manuscript received October 29, 2012; accepted March 16, 2014.


Does this implies that the paper is directly accepted?
Not necessarily. Some journals only state dates for submission and acceptance. In such cases dates for revisions are not mentioned. Since it is not uncommon, at least in fields with which I am familiar, for papers to go through two (or sometimes more) revisions, a date for revision usually refers to only one, the first set of revisions.

I can also confirm Anonymous Mathematician's notion that some journals only accept papers that receive minor revision and reject those with major, but with the explicit understanding the paper should be resubmitted once revised. This will officially shorten the times from submission to accept but is of course a questionable action to manipulate such statistics.