Years from now, residents of San Jose will tell their children and grandchildren about simpler times—when phoning a neighbor meant punching in seven digits. Those will have been the days. When we were a community that rallied around a single area code. But starting Saturday, the laborious and confusing process of using 11 digits starts, as a new area code—669—is introduced to the South Bay.

The new area code, which joins the traditional 408, was created by the CPUC (California Public Utilities Commission) to meet increasing demand for telephone numbers, no doubt caused by the influx of cell phones in the last 20 years.

On Saturday, all local calls from the 408 area code must be dialed using 11 digits, 1 + area code + seven-digit telephone number. For example: 1-408-867-5309.

The 408/669 area code overlay covers Santa Clara County, as well as neighboring cities and small unincorporated portions of Alameda and Santa Cruz Counties. Primary cities that will use the 408/669 area codes include San Jose, Campbell, Cupertino, Gilroy, Los Gatos, Milpitas, Monte Sereno, Morgan Hill, Santa Clara, Saratoga, Sunnyvale, and portions of Palo Alto and Fremont.

The real culture shift begins in November, though, when all new numbers issued in the South Bay will include the 669 area code.

You’ve been warned. Act accordingly.