Filing Date for 2020 1040's

[RWG1950]

Was the filing deadline for 2020, 4-15-2021 or was it 4-18-2021 ? Or was it the later Covid date. Can't seem to remember this.
Whatever the date, would it then be used to begin the normal 3 year statute of limitations for amending to claim a refund ?
Thanks for comments

[New York Enrolled Agent]

Was the filing deadline for 2020, 4-15-2021 or was it 4-18-2021 ? Or was it the later Covid date. Can't seem to remember this.
Whatever the date, would it then be used to begin the normal 3 year statute of limitations for amending to claim a refund ?
Thanks for comments

See Notice 2023-21 - it gives all the details.