Why we use 'on' because I thing 'in' is also right

[Kothow]

English Language Tests, Intermediate level

ESL/EFL Test #203 "Prepositions of Time and Date (1)", question 10

I'm going to my parents' house in Maine. What are you doing ......... Christmas Day?

(a) on
(b) in
(c) with

English Language Tests, Intermediate level

ESL/EFL Test #203 "Prepositions of Time and Date (1)", answer 10

I'm going to my parents' house in Maine. What are you doing on Christmas Day?

Correct answer: (a) on

Your answer was: incorrect
I'm going to my parents' house in Maine. What are you doing in Christmas Day?
_________________________

Sir why we use 'on' because I thing 'in' is also right.

Kothow

[Pamela]

Special dates and festivals are used with the preposition on