He is the first, He comes first, He is top of...
It is the first of August.
El es primero in English means the first is.
The first of August.
Today is July First
It's the first of September
Hoy es el primero de mayo
Today is the first of March
It means "My mother's birthday is the first of June."
Es el primero de noviembre de dos mil diez.
Es el primero de septiembre.
"Es el primer día de la escuela" means "It's the first day of school", or as a question, "Is it the first day of school?"
You would say "el veinticinco de enero". Remember that the names of the months are not capitalized in Spanish.