howa said:
or why should I use gMonth in the schema?
You asked what the Schema-standard way to represent a month is.
gMonth is it.
You use it the same reason you use other schema types -- because you
want schema to check that it's in the right range, and/or because you
want schema-aware applications to automatically do something reasonable
with it.
I can just simply use a integer or string.
You certainly can. You can even use an integer that's limited to the
1-12 range, or a string that is one of a limited set of values, if you
set the schema up appropriately. But then nobody but you knows what its
semantic meaning is. That may or may not matter to you, depending on
what you're doing with the data now and what you intend to do with it in
the future.