Changing the date/time a picture was taken on iPhone 5?

Not too long ago, I updated to iOS8 and ever since then, the pictures on my camera roll or "recently added" got all switched around and everything is backwards/in the wrong places. For example, photos I just took before I updated to iOS8 are at the very beginning of the "recently added" album on my phone, and photos I've taken 2 years ago are showing up at the end of the "recently added" album on my phone. It's also very random with some photos, there's no specific order they got switched to. What I'm wondering is, is there a way to change the dates of the photos I've taken in the "recently added" album so I can re-organize them so they're all in the right order again?

Have you actually checked the dates to see if they are wrong? By any chance were you using a different date format before - DD/MM/YY vs MM/DD/YY as in different parts of the world?