[Grammar] The following day is incorrect?

[eggcracker]

I searched on Google because of grammar about 'reported speech'. The left on below is what typed. I understood I did mistake or error about the word 'will' and it should be 'would', but isn't it correct to change 'tomorrow' into 'the following day'? I learnt 'the following day' and 'the next day' are both unobjectionable when changing sentence structure like this before from a book.

5) Emily:"Our teacher will go to Leipzig tomorrow." Emily said that her teacher will go to Leipzig the following day..

Correct answer: Emily:"Our teacher will go to Leipzig tomorrow." Emily said that their teacher would go to Leipzig the next day

Sources from Reported speech - statements with expressions of time - English

 

[Barb_D]

There is no difference between "the following day" and "the next day" in this context.