While it can take the IRS up to 48 hours to process and accept a return, the important thing is the Post mark. Just like when you mail in a return, as long as it's postmarked by the deadline (even though the IRS won't receive it for a few more days) it will be considered to be filed on time.
The same thing applies when you e-file your return. As long as you transmit your return before the deadline (the electronic post mark) your return will be considered to be filed on time.
And don't worry, if for some reason your return is rejected, you'll have another 5 days to make any necessary corrections and file it again, and it will still be considered to be filed on time.
While it can take the IRS up to 48 hours to process and accept a return, the important thing is the Post mark. Just like when you mail in a return, as long as it's postmarked by the deadline (even though the IRS won't receive it for a few more days) it will be considered to be filed on time.
The same thing applies when you e-file your return. As long as you transmit your return before the deadline (the electronic post mark) your return will be considered to be filed on time.
And don't worry, if for some reason your return is rejected, you'll have another 5 days to make any necessary corrections and file it again, and it will still be considered to be filed on time.