This weekend, from April 19th until the 22nd, Microsoft is unlocking every Xbox silver account in the US, Canada, Latin America, and Japan, and turning them into Gold accounts.
During this period all Xbox owners will have access to all the benefits that Xbox Live Gold membership has to offer. This means that you can play online with any game (e.g., Call of Duty Ops II, FIFA 2013, Assassin’s Creed 3, Far Cry 3, and more); you’ll have unlimited access to Xbox apps such as Netflix, Internet Explorer, YouTube, SmartGlass, and many more — Just to be more specific, the free access will run until Monday, April 22nd at 1PM Eastern Time or 10AM Pacific Time.
Enjoy!
Source Major Nelson