Google’s Calendar app is pretty fantastic. It integrates cleanly with Gmail, it’s well-designed and organized, and the mobile apps are top-notch. To make it even better, the Gmail team is adding holidays from 30 new countries to their Calendar app, ranging from Australia to Brazil.
Like all Google improvements, this update is going to roll out in phases over the next few days. If you’re itching to put another country’s holidays in your calendar, just hang tight for a few days until you see the update.
source: Gmail Blog