User blog:YokelBellic/Grand Theft Auto Online - Down For Maintenance

Just in case you haven't heard already, GTA Online is down for maintenance from 9pm Eastern Time to 16 January 2014, the servers should be back up and running in the evening, or 5-9pm EST.

Update: Servers are back online as of 16 January, 3pm EST.

Source: http://www.rockstargames.com/newswire/article/52085/grand-theft-auto-online-maintenance-period.html