Celebrated every year on January 1
Creative works enter the public domain when copyrights expire.
Public domain means literally that these works are owned by everybody and can be used by anybody without having to pay any legal fee and without any other restrictions.
This legal transition of copyright works into the public domain usually happens every year on the first January based on the individual copyright laws of each individual country.
The time it takes for an intellectual property to enter public domain is 50 or 70 years after the death of the creator.
But some countries may use other criteria.