[Grammar] expressing future facts

[aggiesteph]

One of English textbooks for Polish high school students instructs them to:

use "will" when referring to a future fact

e.g. Anna will be 18 next week.

Then there is an exercise in which students are supposed to correct the mistakes. One of the sentences is:
"Next year February will have 29 days". The teacher said it is wrong, and it should be:
"Next year February has 29 days".

Does the original sentence really need correcting? Because I understood it as a future fact, just as in the example with birthday.

 

[bhaisahab]

"Anna will be 18 next week."
"Anna is going to be 18 next week."
"Anna is 18 neet week."
"Anna turns 18 next week."
"Next year February will have 29 days."
"Next year February has 29 days."
All of the above are correct.