IOI 2018 took place in Japan in September, 2018. More info is available on the official website.
Just happened IOI 2018 in Japan
Croatian Open Competition in Informatics
The fourth contest will be held on Saturday, 16th December 2017, starting at 14:00 (GMT/UTC). Check out your local times at http://hsin.hr/coci/next_contest.html.
You may use Python, Pascal, C, C++ or Java as your programming language of choice.