5 things you need to know this weekend

1. The ninth edition of Earth Hour will roll across the globe

At 8:30 p.m. on Saturday, people and public places across the globe will switch off their lights for one hour to raise awareness about the impact of energy use on climate change. Families and organizations are encouraged to turn off the lights and other unnecessary electrical devices from 8:30 to 9:30 p.m. local time in order to participate in the global Earth Hour campaign, organized by the World Wide Fund for Nature (WWF). Earth hour began in Australia in 2007 and is now celebrated in over 150 countries around the world.

2. March Madness continues with Elite Eight games

They call it March Madness for a reason. Is your bracket busted yet? It's been non-stop hoops since four teams punched their tickets to the Elite Eight on Thursday (four more did the same Friday night.) The men's action starts all over again Saturday, when No. 2 Arizona plays No. 1 Wisconsin in the West Regional final (tipoff at 6:09 p.m. ET). Arizona played Wisconsin — and lost by one point in overtime – in the West Regional final last year in Anaheim. The Wildcats are hoping to reverse that trend. Women's games start at noon, when No. 1 Connecticut takes on No. 5 Texas in Albany. There's a full slate of mens' and womens' games both Saturday and Sunday, as teams try to earn a spot in next weekend's Final Four in Indianapolis.

3. AA to absorb US Airways' frequent-flier accounts as merger continues

Travelers will see the most tangible sign yet of the US Airways-American Airlines merger this weekend when US Airways' frequent-flier program is absorbed into American's. US Airways' Dividend Miles program will fade into history as members' miles are automatically transferred into American's AAdvantage program beginning Saturday. The transition is a major merger milestone for the carriers, who combined in December 2013 but still have separate operations.

4. Crucial presidential vote in Nigeria, Africa's richest nation and its largest democracy

Nigerians head to the polls Saturday in what analysts say will be the most tightly contested presidential election its history. President Goodluck Jonathan, who is running for re-election, urged peace as ballots are cast. Former military dictator Muhammadu Buhar is his main challenger. This election is only the eighth since Nigeria's independence from Britain in 1960. No incumbent has ever lost. The election is taking place in the shadow of the Boko Haram Islamic uprising. Jonathan has been dogged by the incident in which 300 schoolgirls were kidnapped from a boarding school almost a year ago; 219 of them remain missing. Nigeria's military on Friday claimed it destroyed Boko Haram's headquarters in Gwoza, but that claim, which came ahead of Saturday's critical election, couldn't be independently verified.

5. The fan-voted music awards are back

The second-go-around for the iHeart Music Awards return Sunday (NBC, 8 p.m. ET/PT) from Los Angeles' Shrine Auditorium. The three-hour, performance-heavy ceremony honors the biggest artists and songs of the past year, as determined by the iHeartRadio music chart and fans nationwide, according to a release. Last year's telecast with performances by Ariana Grande and Ed Sheeran drew an audience of more than 5.5 million viewers, with more than 65 million votes cast by fans on Twitter and Facebook. This spring's awards will broadcast live simultaneously on iHeartMedia stations across the USA, as well as on the iHeartRadio digital music platform.

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