If I am a future teller and made a prediction yesterday about something two days in the future, how do we use tenses here?

Question

I happened to imagine this particular situation, which is quite unreal. But I am curious how we use verb tenses to describe the situation.

Let's say I am future teller. I can tell the future. One day I write down what my girlfriend will say two days in the future. And I tell this to my friend one day later.

I know it is confusing. Let me put it in a simple way like this.

5/24 - Me writing down the words my girlfriend will say on 5/26.

5/25 - Me telling to my friend about the prophecy.

5/26 - The date when my girlfriend says what I have predicted.

My question is here: the conversation happens on 5/25.

1. Me: Hey, mate. Yesterday I wrote down what my girlfriend will say.
2. Me: Hey, mate. Yesterday I wrote down what my girlfriend would say.

Which one is correct?

Answer 1

(Yesterday) I wrote down what she will say (tomorrow).

There is a misconception sometimes expressed here that subordinate clauses in a sentence must have the same tense as the main clause. This is often the case, but it is not a grammatical rule, just that, usually the time referred to in the subordinate clause is the same as in the main clause.

But there are plenty of examples where this is not true, and the "fortuneteller" example is one example.

Using "would" is also possible, but this suggests some condition that is unspoken or implied:

... what she would say tomorrow [ if ...]

You can also use other future constructions

... what she is going to say
... what she says when she first sees me tomorrow.

Answer 2

Considering the grammatical timeline set by the main verb (past tense), the choice of “would” could be better, due to the corresponding verb tense agreement. Besides, “I wrote down what my girlfriend would say” could mean talking about the future in the past, and the usage of the word “would” seems more appropriate.