Tom: I will phone you on Sunday.
Me: Tom said he would phone me on Sunday.
I decided I will go to the library. (today)
I decided yesterday I would go to the library. (tomorrow)
Do I always have to change will to would when put a statement in the past? What if I say: “I decided yesterday I will go to the library.” or “Tom said he will phone me on Sunday.”
It is permissible (but not obligatory) to use will in these circumstances if it refers to an event which is still in the future at the time the sentence is uttered.
If on Friday you decide that you will go to the library on Monday …
- You may say I decided I would go to the library on Monday at any point after your decision.
- You may say I decided (or have decided) I will go to the library on Monday at any point after your decision right up to whatever point marks the end of any practical opportunity for going to the library on Monday.
- After that point you must say I decided I would go to the library on Monday.
Source : Link , Question Author : Graduate , Answer Author : StoneyB on hiatus