Sync issues with iCal on iPhone/iMac

I have recently picked up an iPhone 5, running iOS 6.1. I also run an iMac (circa late 2008) which is running Snow Leopard, so no iCloud integration. I am trying to sync the iCal's on both devices, and I am seeing the following behavior: If I create an event on my iPhone, and then "Sync" manually using iTunes, then the new event appears on my iMac, but not the other way around, i.e. I tend to use my iMac as the Master calendar, so I would like to create an event on my iMac, and then have it appear on my iPhone when I "Sync", but I can't seem to make this happen. So, the Sync behavior seems unidirectional, from the iPhone to the iMac only, but not the other way around.

I have selected the "Sync this phone with Wi-Fi" option on the iPhone->Summary tab and the "Sync Calendars" option on the iPhone->Info tab in iTunes.

Does anyone know how to make the iCal sync-ing be bi-directional (or barring that, uni-directional the "other" way) ?

Thanks in advance.