Why is it that some temporal nouns cannot be marked with に? And why do they become more acceptable with には? Consider the following: here is used in its function of denoting the time where an event occurs (1): * 1 * 1 * 1 * 1 * * 1 * ?/ * * 1 * ?/ * * 1 * ?/ * * 1 * ?/ * * 1 * ?/ * * 1 * ?/ * * 1 becomes acceptable if dative(2): * 2 Why is it that may not be used for the instances marked with * ? Why is acceptable? If 1 is prohibited but allowed, does this suggest that the of is distinct from 1? I think 1 may not be used to mark deictic (words which meaning depends on contextual information) nouns. I think that is what they have in common. It is not possible to have useful information about "yesterday", "today", "tomorrow" or "next year" etc. unless we have more information about the current time.

Good observation that you mention deictic expressions. That is correct. Deictic pronouns with accusative case tend to be used adverbially rather than as pronouns; they already incorporate the meaning of `on` or ``, so it would be redundant to have another ending. In traditional grammar, this is called _adverbial accusative_ or _adverbial objective_. Latin clearly had an overt marking for this.

As for ``, it means a different thing. It means "by", and that will not make the expression redundant.

> * on today
> by today
> *
>