Wikipedia, in "New riddle of induction", sets out Nelson Goodman's paradox as follows:
Goodman defined grue relative to an arbitrary but fixed time t as follows: An object is grue if and only if it is observed before t and is green, or else is not so observed and is blue. (note omitted)
In Goodman's definition, does the observer know whether Time t has passed? It would seem that the observer could not know. Assume t is known. If t has not passed, the timing leaves open the possibility that the object is grue, but allows the observer to simply wait until the clock reaches t and answers the question; and if t has arrived or passed, the open possibility is closed and the question resolved.
Has any analyst answered this? At the beginning of observations, does the Observer know Time t?