iphone calander + sign grayed out

In my iPhone calendar, the "+" sign is grayed out and will not allow me to add an event. I have tried going to calendars in iCloud (settings/icloud/turn on calendars)and calendars was on, so I turned it off, waited a few sec. and turned it back on, no success. I closed all programs and rebooted the phone and still not able to add an event into calendar, also went to settings/mail,contact,calendar and all is on there as well.