iphone calendar won't sync

I am using an iphone 5 and syncing with my iMac via USB cable. Recently when I sync new calendar dates added to the iphone do not appear on the iMac calendar. I did not make any changes in hardware or software. I have already checked on the itunes page that sync calendars is checked,

Depending on what OS version you are using on your Mac, you are probably better syncing your calendar via iCloud now. That would keep the calendars sync'ed over the air.