Why is "that" used here as the relative pronoun instead of "when"?

Question

This sentence from an article strikes me as somewhat unusual. Since the modified antecedent is a point in time, why is "that" the relative pronoun instead of "when"?

I met Jonathan Annicks shortly after the night two years ago that he was shot sitting in his brother’s car outside his home.

Also, can the relative pronoun in this situation be omitted? Namely, can I write a sentence such as:

I met him shortly after the night he was shot.

This sentence reads totally fine to me, but according to several online sources the relative pronoun can be left out only when it is the object of the verb in a defining relative clause, but this sentence doesn't seem to be such a case.

Answer 1

"That" is optional at the start of any relative clause that contains a separate explicit subject. Since that relative clause in the quoted sentence has "he" as the subject, the word "that" is optional. "That" is only mandatory when there is no separate phrase serving as the subject, as in "This is the man that was shot". (Traditionally, "that" was analyzed as a relative pronoun and treated as the subject of relative clauses like this. A more modern analysis treats "that" as a "subordinator" rather than a pronoun.)

The reason "that" can be used instead of "when" here is because "the night two years ago" is a special kind of noun phrase. Certain nouns, such as "night", can be used in noun phrases that function adverbially without any preposition: for example, we can say "He was shot that night sitting in his brother’s car outside his home."

When a relative clause after a noun like this is used to describe something that happened at that time, it's possible to use "that" (or to leave it out) instead of using "when". Examples (with a corresponding non-relative sentence in parentheses):

• "That was the day that I arrived." (I arrived that day.)
• "2005 was the year that they divorced." (They divorced that year.)
• "That was the moment they won the game." (They won the game that moment.)

Answer 2

"that" and "when" are interchangeable in the first sentence. Which night was it? "The night on which he was shot" "The night that he was shot" "The night when he was shot" all work.

As for your second question: In your example, you can leave the pronoun out. The original sentence can't. Why? Because of "two years ago". If you try to leave the pronoun out of the original sentence, you get

"the night two years ago he was shot" which is clearly incorrect. You could rearrange it, however, and make it "the night he was shot, two years ago".