We use tomorrow’s meeting to describe a meeting that is held tomorrow. Tomorrow’s meeting is correct.Tomorrows meeting is incorrect.
We need the apostrophe s to show the possessive form. This means that the meeting belongs to tomorrow. The two words(tomorrow, meeting) are connected.
Tomorrows(without the apostrophe) is not grammatically incorrect but it isn’t common in English. Tomorrows is the plural of tomorrow but tomorrow is usually singular(it is one day)
Why is it Tomorrow’s meeting and not Tomorrows meeting?
We use the apostrophe s to show that the meeting and tomorrow are connected. Tomorrows without the apostrophe is the plural of tomorrow.
The plural of tomorrow is not very useful in English because there is only one tomorrow. The only example I can think of where tomorrows is used is for the idea that you will have many tomorrows which means there will be more time in the future.
This is probably a more poetic form of English and not common in regular English. One example is Frank Sinatra’s song “All my Tomorrows”.
More examples of Tomorrow’s
I need to prepare for tomorrow’s meeting. It starts at eight.
What time does tomorrow’s concert start at?
Tomorrow’s weather looks nice.
What is tomorrow’s class?
Tomorrow’s morning meeting or Tomorrow morning’s meeting
Tomorrow’s morning meeting is more common when there is also a meeting in the afternoon and you want to avoid confusion by saying it is the morning meeting and not the afternoon meeting.
Tomorrow morning’s meeting is a common way to describe a meeting that is happening tomorrow morning.
To avoid confusion, you can just say:
There is a meeting tomorrow morning at 9am.