The I.R.S. confirmed it would push back Tax Day by one month. The new deadline will be May 17, two days later than a congressional aide initially said.

Wednesday, March 17, 2021 6:23 PM EST

An aide familiar with the plan initially told The New York Times the deadline was being extended to May 15; that day is a Saturday, and customarily a weekend Tax Day is pushed to the following Monday.
The New York Times