Could we say "His birthday is on the next Saturday?"

[Watie]

English Grammar Tests, Elementary Level

ESL/EFL Test #152 "Dialogue Practice: Buying a Music CD (1)", question 7

Man: His birthday isn't until next Saturday. Do you think the ......... will arrive before the weekend?

(a) shipment
(b) seam
(c) dock
(d) flight

English Grammar Tests, Elementary Level

ESL/EFL Test #152 "Dialogue Practice: Buying a Music CD (1)", answer 7

Man: His birthday isn't until next Saturday. Do you think the shipment will arrive before the weekend?

Correct answer: (a) shipment

Your answer was: correct
_________________________

Could we say "His birthday is on the next Saturday?"

Many thanks for the incoming explanations.

[Mister Micawber]

Not unless the context is also referring to another day of the week or another event on another day.
_________________
Native English teacher at Mister Micawber's