What is the registration date?
Is it when I publish, when I submit, or when the certificate is issued?
Your registration date is when your submittal is received at the Copyright Office.
“When the Copyright Office issues a registration certificate, it assigns as the effective date of registration the date it received all required elements — an application, a nonrefundable filing fee, and a nonreturnable deposit — in acceptable form, regardless of how long it took to process the application and mail the certificate.”
— U.S. Copyright Office, Circular 1
“The effective date of a copyright registration is the day on which an application, deposit, and fee, which are later determined by the Register of Copyrights or by a court of competent jurisdiction to be acceptable for registration, have all been received in the Copyright Office.’
— U.S.C. Title 17 §410(d)