September 11, 2012: Armed gunmen storm the American consulate in Benghazi, Libya, and kill U.S. ambassador to Libya Christopher Stevens and three other embassy officials.

November 6, 2012: President Obama is re-elected, narrowly defeating Republican nominee Mitt Romney.

April 15, 2013: In Boston: Two pressure cooker bombs explode at 2:49 p.m. near the finish line of the Boston Marathon. Three people are killed and another 264 people are injured. A manhunt and lockdown of Boston follows as police search for the Tsarnaev brothers.

June 25, 2013: In Shelby County v. Holder, the Supreme Court strikes down Section 4 of the Voting Rights Act.

July 13, 2013: A jury in Florida finds George Zimmerman not guilty of murdering unarmed black teenager Trayvon Martin as a result of the Stand-Your-Ground law.

February 2014: The Ebola virus epidemic in West Africa begins, infecting over 28,000 people and killing at least 11,000.

June 11, 2014: Members of the Islamic State of Iraq and Syria (ISIS) take control of Mosul, in northern Iraq.

August 9, 2014: Police Officer Darren Wilson shoots and kills Michael Brown, an unarmed 18-year-old teenager in Ferguson, Mo.

January 5, 2015: In Boston: Boston Marathon bombing trial begins.

January 26-27, 2015: In Greater Boston: January 2015 North American blizzard occurs. Boston sets a new city record for snowfall in 2015.