Do I deserve to know the exact timeline?

Wondering if I’m in the wrong here. I want to know the exact length of time the A occurred. When it started(month and year) and when it ended(month and year.) I’ve been made to feel like a rough estimate is acceptable, and I shouldn’t push for the exact dates. The dates I’ve been given have an open end ranging between 1-6 months. Half a year is insane to me. My WH has tried to recall exactly when it ended but can’t remember specifics. He says it’s mentally exhausting to have to jump back into “the worst mistake of his life” to try and remember for me. We are 7 months post dday. I have been patient and given him as much time as he has needed, and he tends to sit in it and not take action.

Should I take the info given so we can move forward? Does knowing the exact dates change anything? Trying to figure out why it’s so important to me.