To your question … consider your audience.

If you are submitting to a job posting, then your resume will be “screened” first. The screener may not know the details of the job, much less the details on your resume. Screeners are looking for reasons to say no. They want to narrow the field down to a handful of candidates … a manageable number. Your resume should be clear and as concise as possible. Months on the dates of service are appropriate. Because you are playing a numbers game, your odds are not good unless you have done the same job in a similar industry with similar technologies. Make sure that your resume isn’t screened out for leaving off dates or not being specific on what you did, for whom, when and the results.

If you are submitting to a recruiter, presumably a good one, also use a detailed resume (with months). A good recruiter will coach you on formatting the resume for their client so that it highlights the skills that the client is looking for.

If you are networking with hiring managers or people who may be able to refer you to a job, use a resume that is concise and that highlights accomplishments; more than a skills list. In this case, you probably can drop the months. Be careful of loading up a resume with buzzwords and lingo when you are networking for a job. The lingo can prevent your non-technical friend from understanding what he or she can do for you.

As a side note, when networking it is probably best to ask for a referrals … instead of asking for the friend to forward your resume for you. I believe that a warm referral gives you a chance to sell yourself. Forwarding resumes around doesn’t.

I hope that you find your dream job!

Also, regarding resume length, when someone has many years experience, how far back should a detailed account go? My resume is five pages, It takes one page alone for an overview and to list all of my skills. Then, there is another 4 pages for experience.