Three month warning
Do you do anything involving seven digit dialing within the 408 area code? Think carefully now. Embedded devices with autodialers, those apartment phones which let you "buzz someone in", security systems and all of that other stuff counts.
How about your advertising? All of those signs, flyers, and yes, even those things twirled by people at intersections frequently sport phone numbers.
This is your three month reminder. Area code 669 is coming.