I've been using an iPhone charger to charge my iPad have I damaged the iPad?

Iv been charging my iPad with my iPhone charger to charge my iPad as I thought there was no difference between them and I could keep the iPad charger as a spare if I miss placed my iPhone charger but I read up that using the wrong charger could mess up the battery if been using the iPhone charger since I have got it iv had it for 5 months from new but today it seem to be taken to long to charge I'm now using the charger that came with the iPad and see how that goes

No not really unless its the iPhone 5. I use my IPad charger for my iPod and ditto it's just the same the thing the only difference is the iPhone 5 is a 4 inch xxxx