https://www.irs.gov/pub/irs-drop/n-20-17.pdf

https://www.irs.gov/newsroom/payment-deadline-extended-to-july-15-2020

Copied from another list I'm on:

April 15, 2020                      File your tax return or submit an extension to file

June 15, 2020                      Your 2nd quarter 2020 estimated payment is due

July 15, 2020                        Your 2019 tax payment is due

July 15, 2020                        Your 1st quarter 2020 estimated payment is due