Which one (#1, #2 or #3) is grammatical?
This is calculated as...
1) ...the price difference from one year to another.
2) ...the price difference from a year to another.
3) ...the price difference from one year to other.
I was about to write #1 in a document, when I thought that maybe I should not mix a numeral (one) with an article (an in another).
UPDATE: In his answer below, FX_ says that he would say #1 and that thinks that #2 is also correct. I'm starting a bounty to check if there any different answers.