This question already has an answer here:
I'm under the impression irony is when the opposite of what you expect happens. Someone dies giving a safety presentation, for example. Coincidental, on the other hand, is when merely something unlikely manages to happen.
Here's the situation: A few weeks ago I wore a pair of jeans somewhere. Today my friend asks what pair of jeans I'm wearing, and it happens to be those. He says how ironic that is. I say it's a coincidental, not ironic.