Project Planning: Percentage Complete from Dates

Can you provide an example of the dates at issue, and what a correct response is?

Because it sounds like you have a schedule baseline, but now we are off of the baseline, so, based on progress to date, you want to calculate an end date. It seems like we are missing a variable, which is how much progress you've made.

For example: If we forecast a task will take from Jan 1 to Jan 31, and I am sitting here on March 1, and you ask me when I will be done, it matters if I am 10% or 90% complete. Because if I am 50% complete, that means that it took me two months to get as far as I baselined I would get in two weeks, so things are taking 4x as long, so I should be done in two more months.