(CNN) -- Saturday marked the start of autumn in the Northern Hemisphere and the beginning of spring in the Southern Hemisphere. CNN celebrated the change of seasons with a global mobile photography project. The challenge was simple: On September 22, 2012, go outdoors and take a photo with your phone. The only requirements were that the photo be horizontal, shot on Saturday and have no filters. The photos were shared on social media with the hashtags #hellofall and #hellospring. We received more than 1,700 submissions from six continents, including plenty of pumpkins and colorful leaves, but also shots of beaches and even one taken underwater! Users uploaded photos to iReport using the CNN mobile apps, via email and on iReport.com. Check out some of the best in the gallery above.
The September equinox began Saturday . Users uploaded photos to iReport, using the CNN mobile apps . The best shots were showcased as part of "Our Mobile Society" initiative .