It is 7 years from the date of charge off. Under the federal law, called the Fair Credit Reporting Act (FCRA), the FCRA enforces the 7 year limit stating that a charged off account or placed for collection must be completely erased after seven years from the date of last activity; last activity generally means the date the creditor charged off the account.
Consumer reporting agencies may not report outdated negative information. In most cases, a consumer reporting agency may not report negative information that is more than seven years old, or bankruptcies that are more than 10 years old.
Here is a link from the FTC if you want to read it more in detail.