SN3 that definition will work in the US, and most other places, I'm not willing to say that it will work everywhere because I simply don't know everything and everyone well enough to bet my word on it, I know US regs. However, even within the US legal system you'll find both definitions as accepted in different cases, you can use a legal dictionary to find this stuff.
Anyone involved with aviation in the US or operating under the FAAs oversight should only comply with the idea that it's the first of a "named" month to the last of a "named" month.