possessive with the time signifiers

[Kotfor]

1) yesterday's newspaper but yesterday morning (why not - yesterday's morning)

2) this morning's newspaper but a morning newspaper (why not - a morning's newspape)

[philo2009]

1) yesterday's newspaper but yesterday morning (why not - yesterday's morning)

2) this morning's newspaper but a morning newspaper (why not - a morning's newspape)

I'm not sure that I, or indeed anyone, can really tell you 'why' usage has developed in this way, but the simple fact is that possessive 's' is not appended to the words 'yesterday' and 'tomorrow' when they determine nouns that denote times of day (morning, afternoon, etc.), while the 's' is obligatory where they determine other, ordinary nouns.

As regards the nouns 'morning, afternoon' etc. themselves, when they function as modifiers (i.e. typically following an article), they are, like adjectives, invariable, and therefore do not take the possessive termination. When, however, they form part of a determiner phrase (as in this morning's, yesterday afternoon's...), the possessive termination is, once again, obligatory.

[Kotfor]

I see. Thank you. It's a difficult subject. What is better?

1) yesterday's morning newpaper or 2) yesterday morning's newpaper

[bhaisahab]

I see. Thank you. It's a difficult subject. What is better?

1) yesterday's morning newspaper or 2) yesterday morning's newspaper

They are both possible.

[5jj]

1) yesterday's morning newpaper or 2) yesterday morning's newpaper

Both are possible with different meanings. #1 refers to the morning newspaper, as opposed to the evening newspaper, that appeared yesterday. #2 refers to the newspaper that appeared yesterday morning.

[Kotfor]

#1 refers to the morning newspaper, as opposed to the evening newspaper, that appeared yesterday. (Was it published yesterday morning?)

#2 refers to the newspaper that appeared yesterday morning. (I don't understand what you mean here. Was it published yesterday morning or a person got a hold of it yesterday morning but ut had been published before?)

Sorry for being a bit slow on the uptake.

[5jj]

#1 refers to the morning newspaper, as opposed to the evening newspaper, that appeared yesterday. Was it published yesterday morning?
Yes. Daily newspapers generally appear on the day of their publication.

#2 refers to the newspaper that appeared yesterday morning.
I don't understand what you mean here. Was it published yesterday morning or a person got a hold of it yesterday morning but it had been published before?

It was published yesterday morning.

There is little significant difference between the two sentences, exept that the first implies more strongly that there may be afternoon/evening newspapers.

[philo2009]

Both are possible with different meanings. #1 refers to the morning newspaper, as opposed to the evening newspaper, that appeared yesterday. #2 refers to the newspaper that appeared yesterday morning.

And, more to the point, with different structures:

[[Yesterday's] [morning newspaper]] realizes the structure [[DET] [ADJ+N]]while

[[Yesterday morning's] [newspaper]] realizes the structure [[(compound) DET][N]]