On whatever local time where you are (at least for US). The "at least in US" is important since that most people who didn't clarify that "Steamboat Willie" is

On whatever local time where you are (at least for US). The "at least in US" is important since that most people who didn't clarify that "Steamboat Willie" is in the public domain specifically in reference to US laws - in other countries it is either already PD, or in a handful countries like Mexico (which has author+100, technically no concept of corporate copyright except for the government) is still not PD.