I have sometimes wished Excel had a global "I prefer things with / to be seen as fractions" setting, because Excel currently just has too much preference for interpreting input as dates.

The easiest approach might be a combination of a function like Alkey suggests and a find replace. I think you will find that the find/replace method works just fine for the values greater than 1, because i n/d type number cannot be readily interpreted as dates, so Excel will naturally want to see those as fractions. A function like Alkey's will then work to fix those that are between 0 and 1.