In Spanish, the months of the year are: enero, febrero, marzo, abril, mayo, junio, julio, agosto, septiembre, octubre, noviembre and diciembre. In Spanish, the names of the month are not capitalized. The months in Spanish are very similar to those in English due to the linguistic similarities between the two languages. Since Spanish and English are both Romance languages, many of the month names are cognates and thus share similar spellings and pronunciations, notes About.com.
In Spanish, the months are also masculine nouns, and therefore take the article "el." However, the months are rarely accompanied by their definite article. Articles are only used when giving specific dates, notes About.com. The seasons, on the other hand, use the definite article.
The more common spelling of the month September is septiembre, however, it can also be spelled setiembre, according to Castellano Actual.
The Spanish way of writing or saying a date differs from English, adds Study Spanish. In Spanish, a date is written as the day followed by the month and then the year, e.g. "el 4 de enero de 2015." Another difference between the two languages is that the Spanish dates do not use commas, adds Spanish 411.
When referencing the first day of a month, the phrases "el primer día" or "el primero" are used rather than the cardinal number, notes Study Spanish.