It really depends. Do you have a good reason for missing 6 years in the workforce? For example, did you take time off to parent a young child? Some places will not necessarily treat that as a detriment, although there is a semi-understandable sentiment at some places that if you took time out like this before you might do it again (I think it's technically illegal to refuse to hire someone on this basis but let's face it - an employer will find 20 ways to not hire you if they don't want you for any reason). Prison? That might be a bit harder to explain.
Can you spin the time off into its own job description? I'm not saying you should turn "parent" or "homemaker" into something - any employer is just going to roll their eyes at that no matter how you happen to feel about those being legit occupations (and for what it's worth, I think they're legit too) - but did you do something else? If you worked outside of the industry, by all means put your work experience there if you think it's at all relevant (i.e. you might want to think twice about putting Domino's Delivery Driver down there if you're applying to work in software development, but customer service for a phone company? Heck yes, put that in there). Realize in this situation that you most likely will be asked why you were out of industry at the time.
Even if you only worked part time, you can surely turn that into a job description. Prospective employers do not have to know that the dog groomer job you had only filled 16 hours of the week.
Is it a job you spent a lot of time at but were fired from in disgrace? I'd still list it. Nowadays from what I gather most prospective employers can only ask the most basic of questions to former ones. In the early 90s they could still ask "would you hire this person again?" but I don't think even that's the case any longer. They can ask "did this person work here between 2004 and 2010?", which is a question which can basically only be answered "yes" or "no". If the old employer volunteers any more information they risk setting themselves up for a lawsuit, or so I am told.
The strategy to not list your year of graduation at all and to just start from your work experience is okay, but there are a couple of red flags. One, HR directors do look over resumes to find keywords and the like but also to look for reasons why to not grant you that interview. For many companies an unaccounted 6 year period is one of them. For several, not filling in date ranges in areas they expect to see date ranges is one. It makes it look as though you're lying or hiding something. Even if you're not, or even if you have really good reasons to do so, a lot of HR people don't know you, don't care, and only really care about whittling down the number of applicants to send to the next level of the interview process.