Student or Learner
Is it correct?
Chinese people celebrate Teacher's Day of September 28th.
In the quoted contex, 'on' would be the preferred preposition.
It is possible and correct to use 'of' before a specific date in the following context:
'The balance sheet, as of December 31, 2005, shows the value of assets...'
indicating the date the particular piece of information refers to.
You can circumvent the problem, if not sure, by saying:
'September 28 is celebrated as Teachers' Day here in China.
All the best,