Guatemala 90 day stay?

I booked my flight a couple weeks ago for a three month trip to Guatemala. I’m super excited and I really hope to reach low intermediate level Spanish. This will be my first trip to Guatemala, but I’ve been to Colombia a number of times, including some Spanish School there last summer.

I’ve booked an Airbnb and a Spanish School for the first month in Antigua and I’m leaving the second two months open in case I want to go to Lake Atitlan and study there, travel around the country, dip over to El Salvador, etc.

Today I realized I actually booked my trip from May 31 to August 30, both Sundays. When I booked it, I thought that it was 90 days but when I counted it out, it’s actually 91. (Insert face palm emoji here)

My ticket is changeable so of course going to the airline is one option. I can’t imagine that they won’t charge me $$ for it though and the ticket was already more than I hoped it would be.

Another option is to apply for the extra day when I’m in Guatemala, correct? I could plan on being in Guatemala City the last couple days of my trip to handle it then.

Thoughts?

¡Gracias!