Dates and Locations After Sync Are Screwed Up

Hi

Recently, I deleted all of my pictures on my phone so I could make a little space for an update to iOS 7.1.2. I imported all my photos to iPhoto on Mac. When the update was done, I went on iTunes 12.1.2.27 and found my phone, then I went to photos and checked the box for sync all photos and videos from iPhoto and I clicked apply. All my photos synced, but for the last 20% of the photos, the dates and locations got messed. That made it so pictures I took a year ago are next to pictures I took recently.

I resynced it, but nothing happened. What do I do?

Thanks,

Zitong