It also depends on your culture. In French the equivalent of `positive` (positif) when used in math means 0 or more, otherwise we use strictly positive. This is different from English (or maybe just US).
Also in Asian countries, your age starts at 1 not 0 (and for some, or maybe it was in the past, you change age at the beginning of the year, i.e. legally everyone's birthday was on January 1st). AFAIK airplanes didn't crash yet due to missed "birthday" maintenance ;).
