Chapter 5-8-13: Future in the Past
WHEN TO USE IT: The future in the past is used to discuss something in the past that you thought would happen in the future. It not important if you were correct or not or whether the action ultimately ended up happening. Use future in the past to discuss a plan or a promise that was made in the past. Or, for a more precise but complicated explanation, SIL explains that "[f]uture-in-past tense is an absolute-relative tense that refers to a time located in the future, relative to a contextually determined temporal reference point that itself must be located in the past relative to the moment of utterance."
FORMS: [would + VERB] or [was / were + going to + VERB]
The "would" form is used when volunteering or making promises. The "was / were + going to" form is used when making plans. Sometimes, either form can be used.
I thought that you said that you were going to be at last night's party. I didn't see you there.
I was going to go, but my dog fell sick and I had to look after it.
We thought everything was going to be all right, but we couldn't have been more wrong.
Oh. I'm sorry to hear about that. Mary promised me that she would go to that same party, and I didn't see her there, either.
She told me the opposite. She said that she would not (wouldn't) go because Steve was going. Mary hates Steve.