Each round of short-term competition lasts from 1 to 5 hours. Long-term competitions can last from a few days to a few months.
The programming community around the world has created and maintained several internet-resources dedicated to competitive programming. They offer standalone contests with or without minor prizes. Also the past archives of problems are a popular resource for training in competitive programming.
On-site events and online links to all competitions and platforms
AI competition with a special attention to Machine Learning