I waited until the last minute to efile. Then Turbo tax told me that I have to mail in my return as well. It's too late to make it to the post office before midnight. So am I late since I efiled in time, but I did not mail before midnight.
You can file an extension, and then mail the return tomorrow. Don't forget to pay any tax you owe today!
but to be timely the extension must be postmarked 4/15.