There are many security events that are run around the world I have mainly listed the most common ones in Europe and the biggest ones. (New Dates will be added once announced)

UK Events
44Con London
 August 30th РSeptember 2nd
BsideLondon April 29th
RSA Europe
Electromagnetic Field Friday 31st August – Sunday 2nd September

USA
Defcon 19

Black Hat Training: July 21 – 24 Briefings: July 25 – 26
BSides

Paris
Nuit Du Hack

Netherlands
DIMVA

Black Hat Europe March 14 – 16,

Spain
Source Barcelona

Brussels
BruCon

If you are interested in other Events around the world check out Ethical Hacker Network Calendar and secore.info