How do I stop a spread sheet from auto correcting to a date?

I want to turn off auto-correcting to dates. I have been using spreadsheets for years and never, not once, have I ever used or wanted a date. I want the cell to compute an equation. I want to put in =3/12, or =6/12, or =9/12 equations and have it return an answer of .25, 0.5, or .75 instead of an auto-corrected date. I do not want to use ' because it will keep the fraction text instead of returning an answer from the equation, it would be the same thing if I changed the cell to text, it will no longer calculate an equation. I have put an equal sign in front because that is usually how you indicate that you want it to be an equation, but it still changes the equations to dates. Other equations work and when I put these fractions inside of other equations they work, but they do not work as stand-alone equations, neither does =90/3 or any other. They all get turned into dates and I need them to be used as equations. And yes, I need to be using a spreadsheet and yes, I want to use Open Office. I just want to know how to get it to do what I want it to do. Please Help. I have seen other forums on this topic and many arguments have ensued for no good reason. I just need help with this one simple thing, thank you.