Date – month and day – in Spanish

I don’t need the plugin to be translated like in the admin or anything, I just need the month and days of the week to display in Spanish. How can I do this? I’ve tried adding setlocale(LC_ALL, ‘es-MX’) to the simple-events-calendar.php file but that didn’t work.

https://www.ads-software.com/plugins/simple-events-calendar/