The competition this post is referring to was during the summer for a local math club in the East Coast.
We do have regular monthly competitions that you can join! In fact we just had one this weekend. Next ZIML competition is coming up the first weekend of November (November 2 to November 4). It is an online competition so you can join from anywhere in the world, and it only requires one hour of your time during the weekend it is open.
The November competition will be available for registration starting October 15. Under "Monthly Contests" you'll be able to find the 5 divisions you can register for.