You must have scheduled your extension payments or balance due payments way in advance.  When I am filing a balance due return on April 15th at 11:00 pm, there is no way under the sun it is coming out on the 15th.  It seems most of my clients returns who owe anything significant don't get me their info until late anyway, and aren't returning to me the signature forms until the 14th or the 15th so it is quite common to file the balance due returns on the last day and not see the money come out for several days.