5 Fridays, 5 Saturdays, 5 Sundays in one month

I was just watching the local TV news and the news guy told the weather man that he heard 5 Fridays, 5 Saturdays, 5 Sundays in one month only happens once every... I forget if he said 600 or 700 years. He stated that he hadn't done research to see if it's true or not. Just for the fun of it I decided to do some research on it and I found one web site that says it happens all the time. They even include pics of calendars from other recent years that have this. I continued to search a bit more and found other sites that say the same thing.