I completed my tax return on the 15th but a print out shows that the electronic postmark was the 16th. After that it was rejected. Why was it postmarked after the date?

 

Get your taxes done using TurboTax

It's likely because of time zone differences.  As long as you filed your return before midnight in your local time, then your return is considered timely filed.  And, you have until April 20th to resubmit your rejected return.