My iPhone 6’s battery has been draining faster and faster over the last couple of months, to the point where it was down to 50% by noon. I did some looking into the usage stats (Settings -> Battery -> Battery Usage By App) and saw that the Calendar app was gobbling up 54% of the available power. I read up and realized Exchange (my work email account) was at fault and followed some directions to turn off Push notifications—even though I don’t allow them to show up on my home screen—and set everything in my mail settings to Manual updates.