Some months after taking a new job I met some of my then ex co-workers for a beer and one of them asked what was I working on in my new job. Among other things, since I was using VMware appliances for both test and build environments, I told him I was working with virtual machines. So he replied 'Ah, so you're working with Java'. The only virtual machine he ever heard about was the JVM.
This is just an example, but in a general way my knowledge about software development technology and tools was deeper than his. In spite of that, his working experience was 2 or 3 years longer than mine. I also know people who has deeper knowledge than mine and have less time of experience.
So my conclusion on this was that any time you read in a resumé 'X years experience in Y', you should take it for 'X years seniority in Y'. So experience means the length of time that someone has been practicing or just in slight contact with a given technology or tool. In a resumé, experience and expertise have little to do.
In one of my recent readings (Rework) there is a section dedicated to this subject. It is pointed out there with this words:
How long someone's been doing it is overrated. What matters is how well they've been doing it.But how can you get to know it?