Most of you would probably know but those who don't know its about you: Internet Problem Solving Contest is an online programming competition for teams of up to three people, conducted annually in May or June since 1999. It is organized by the students and faculty members of Faculty of Mathematics, Physics and Informatics of Comenius University in Bratislava, Slovakia.
Register yourself at: http://ipsc.ksp.sk/
Timing: IPSC 2015 will take place from 20 June 2015, 11:00 UTC to 20 June 2015, 16:00 UTC. The practice session runs from 19 June 2015, 9:00 UTC to 20 June 2015, 9:00 UTC.
More about this can be found here