'Tomorrow evening' vs 'In tomorrow evening'

[Matvej]

English Language Tests, Intermediate level

ESL/EFL Test #206 "Prepositions of Time and Date (4)", question 8

......... tomorrow evening, we're going to have a surprise birthday party for Mitch.

(a) (none)
(b) About
(c) In

English Language Tests, Intermediate level

ESL/EFL Test #206 "Prepositions of Time and Date (4)", answer 8

Tomorrow evening, we're going to have a surprise birthday party for Mitch.

Correct answer: (a) (none)
_________________________

why there are no prepositions in this sentences

Matvej

[Conchita]

The preposition 'in' is not used before words such as tomorrow, today or yesterday. However, the preposition is needed in time phrases like: in the evening or about noon/midnight.

'About tomorrow evening' is grammatically correct if you are not sure of the time. In the test sentence however, the date and time of the party have already been decided.