Quick answer
Hoy es lunes. El concierto es el 3 de mayo.
Today is Monday. The concert is on 3 May. Spanish writes days and months in lower case, and the week starts on Monday.
The words of this lesson
Lower case, always
The days are lunes, martes, miércoles, jueves, viernes, sábado, domingo and the months are enero, febrero, marzo, abril, mayo, junio, julio, agosto, septiembre, octubre, noviembre, diciembre. None of them is capitalised in Spanish, not even at the start of a date. English speakers write Lunes out of habit; it is simply wrong.
A Spanish calendar also starts the week on lunes, so el fin de semana sits at the end, where the name says it is.
"On Monday" without a word for "on"
Spanish uses the article instead of a preposition: el lunes means "on Monday" and los lunes means "on Mondays", every week. So trabajo el sábado is this coming Saturday, while trabajo los sábados is a routine. Adding en before the day is a direct translation from English and does not exist.
The five weekdays do not change in the plural — los lunes, los viernes — while sábados and domingos take an s.
Dates
A date is built with de: el 3 de mayo de 2026. The day comes first, the month is not capitalised, and you use ordinary numbers, not ordinals — el dos de marzo, never "the second". Only the first of the month sometimes takes el primero de enero, mainly in Latin America; Spain says el uno de enero.
Where you are matters
For the first of the month Spain normally says <span class="es-inline">el uno de mayo</span>, while most of Latin America says <span class="es-inline">el primero de mayo</span>.
Memory trick
No capitals, no "en": el lunes already contains the word "on".
A short dialogue
Typical mistakes
Trabajo en lunes.
Trabajo el lunes.
Spanish marks "on a day" with the article el, not with the preposition en.
Mi cumpleaños es el 9 de Agosto.
Mi cumpleaños es el 9 de agosto.
Months and days are never capitalised in Spanish, even inside a date.
Es el tercero de mayo.
Es el tres de mayo.
Dates use plain numbers; ordinals are only used, optionally, for the first of the month.
Practice
Practise these days and months
0/8 matched — tap a Spanish word, then its translation
Check yourself
Which sentence is written correctly?