7.5 Indicating unknown values
When the inclusion of data is mandatory for a particular element in an NFT standard message but a message sender cannot provide such data, the following values shall be entered:
In cells where the data is meant to be a string:
#unknown#;
In cells where the data is meant to be a date:
9999-01-01;
In cells where the data is meant to be a datetime:
9999-01-01T99:01:01; and
In cells where the data is meant to be a duration:
PT99H01M01S.
The circumstances under which such behaviour is permissible is determined by the terms of the bilateral agreement agreed between the message sender and the message recipient.