[Grammar] Teachers’ Day today is the first that preschool teachers get to celebrate.

[kadioguy]

In Lee Hsien Loong's Facebook, he says:

Teachers’ Day today is the first that preschool teachers and early educators get to celebrate. It is an overdue show of our appreciation, but one well deserved. Happy Teachers’ Day, and I hope you have a good break!
-----

1.
Is 'preschool teachers and early educators get to celebrate' an appositive to 'the first'?
Or is it an adjective clause modifying 'the first'?

2.
I wonder whether I should use 'the' in 'In Lee Hsien Loong's Facebook', ie 'In the Lee Hsien Loong's Facebook'.

Would you be so kind as to help me?
Thanks!

PS I also posted the same question on this, but all of your answers are unique to me. Hope we can discuss with each other. Thank you.

 

[Matthew Wai]

Mister Micawber there said the clause is adjectival.
I want to add that 'an adjective clause is also called a relative clause'—quoted from http://grammar.yourdictionary.com/parts-of-speech/adjectives/adjective-clause.html

 

[Matthew Wai]

Is 'preschool teachers and early educators get to celebrate' an appositive to 'the first'?

I think the red part below is an appositive to 'Teachers' Day today'.

Teachers' Day today, the first that preschool teachers and early educators get to celebrate, is an overdue show of our appreciation ...