relative adverb?

[Progress]

I would like to ask native speakers of English.

A friend of mine named Paul received an automobile from his brother as a Christmas present. On Christimas Eve when Paul came out of his office, a street urchin was walking around the shiny new car, admiring it.

Is the when a relative adverb whose head(antecedent) is Christmas Eve and modify Christmas Eve, or just a conjuntion?

Similaraly, On sundays when I was a child, my mother would make cakes.

[David L.]

In this sentence, "when" is a conjunction. Look at these sentences:

...as a Christmas present. When Paul came out of his office, a street urchin was walking around the shiny new car, admiring it.

...as a Christmas present. When Paul came out of his office on Christmas Eve, a street urchin was walking around the shiny new car, admiring it.

...as a Christmas present. On Christimas Eve, Paul came out of his office, and a street urchin was walking around the shiny new car, admiring it.
("and" is also the conjunction here.)

[Progress]

Thank you very much, David L.

I understand that. I thought if when modiies Christmas Eve, its meaing is somehow strange.

How about "On sundays when I was a child, my mother would make cakes?"

[David L.]

Gramatically correct, but note:

"On Sundays, when I was a child, my mother would make cakes."