I would argue against that approach. Make it a requirement that a given API must be used with correct values.e.g. #hours:minutes: requires hours between 00 and 23 and minutes between 00 and 59.
If you want to convert equivalent time values, use a specific API. For example, many time implementations publicly define a seconds-based API, such as Time class>>#fromSeconds:. You can do the same with your implementation with a class-side #fromMinutes: method. (The corresponding instance methods would be #asSeconds and #asMinutes or something similar.)