Learn Hardcore Spanish (Latin America): Según el calendario, la reunión es el lunes por la tarde. - According to the calendar, the meeting is on Monday afternoon.

Days of the week aren’t capitalized in Spanish unless they start a sentence or are in a title. So you write lunes, martes, etc., in lowercase.

Why is it “el lunes”? Does that mean “on Monday”? Could I say “en lunes”?

In Spanish, el + day = “on + day”: el lunes = “on Monday.”
For habitual events, use los + day: los lunes = “on Mondays.”
To be extra specific, you can say este lunes (“this Monday”) or el próximo lunes (“next Monday”).
Don’t say en lunes or a lunes for calendar days; Spanish uses the article, not a preposition.

Why is it es and not está?

For events, Spanish uses ser (not estar) to talk about time and location:

La reunión es el lunes (time of the event).
La fiesta es en mi casa (location of an event). Use estar for the location/state of people and things: La silla está en la sala.

Could I use future será instead of es?

Yes. Será adds a future-looking or scheduling nuance. Es is very common for scheduled events and sounds matter‑of‑fact. Both are fine here.

Why por la tarde and not de la tarde, en la tarde, or a la tarde?

por la tarde = “in the afternoon” (general time period). Neutral and safest across Latin America.
de la tarde is used after a specific clock time: a las 3 de la tarde.
en la tarde is common regionally (Caribbean, parts of Colombia/Venezuela). Understood, but not universal.
a la tarde is Rioplatense (Argentina/Uruguay). If you want broadly neutral Spanish, stick with por la tarde.

Roughly what hours does tarde cover?

It varies by region and context, but think early afternoon to early evening (about 1 p.m. to 6–7 p.m.). To be precise, use:

a primera hora de la tarde (early afternoon)
al final de la tarde / a última hora de la tarde (late afternoon)
Or give a time: a las 5 de la tarde

Is the word order fixed? Could I say the time before the day?

Typical order is day first, then part of day: el lunes por la tarde. Other orders (e.g., por la tarde el lunes) are possible for emphasis, but the given order is the most natural.

Do I need the comma after Según el calendario?

It’s conventional to put a comma after a short introductory phrase like this. You could also place the phrase at the end without a comma: La reunión es el lunes por la tarde según el calendario.

What does según do here, and why the accent?

según means “according to.”
The accent marks stress on the last syllable. Words ending in a vowel, n, or s normally stress the next‑to‑last syllable, so the accent is required to show se‑GÚN.

Why does reunión have an accent, and what gender is it?

It’s stressed on the last syllable and ends in n, so it needs an accent: reun‑IÓN.
Nouns ending in -ión are typically feminine: la reunión, la canción, la decisión.
Plural: las reuniones (the accent drops: reuniones).

Why do we need la before reunión? Can I ever drop it?

Here it’s a specific meeting, so Spanish uses the definite article: la reunión. You can drop the article in impersonal expressions like Hay reunión el lunes (“There’s a meeting on Monday”), where you’re not referring to a specific, previously known meeting.

How do I say “every Monday afternoon” or “this Monday afternoon”?

Every Monday afternoon: La reunión es los lunes por la tarde or … todos los lunes por la tarde.
This Monday afternoon: La reunión es este lunes por la tarde.
Next Monday afternoon (if not the immediate one): … el próximo lunes por la tarde.

Is junta a good synonym for reunión?

In much of Mexico and some Central American contexts, junta is a common word for a meeting (especially work/school). reunión is understood everywhere and is the safest pan‑Hispanic choice. Note that junta can also mean a board/committee in some contexts.

Could I say Según el calendario vs En el calendario dice…? Any difference?

Both are fine. Según el calendario is concise and neutral (“according to the calendar”). En el calendario dice que… is more conversational and explicit (“the calendar says that…”). Style choice, meaning is the same.