What is the statute of limitations for a breach of contract claim?

The longest limitations period available to plaintiffs is four years for the breach of contract claim. ( 337, subd. (a).) The complaint was filed in August 2011. Thus, if plaintiffs' claims accrued prior to August 2007, they are time-barred unless an exception applies. "The statute of limitations usually commences when a cause of action 'accrues,' and it is generally said that 'an action accrues on the date of injury.' Alternatively, it is often stated that the statute commences 'upon the occurrence of the last element essential to the cause of action.'" (Bernson v. Browning-Ferris Industries (1994) 7 Cal.4th 926, 931.)