I have been off the shot for close to 6 years. I received again today my husband wants to know how long it takes to start working?

It becomes effective about 24 hours after it is given. (Source : Family Planning Council: FAQs (http://www.familyplanning.org/familyfaq.shtml#faq2))

However, to ensure that you have the best protection possible, I would use another form of birth control (such as condoms) along with the Depo for the first month.