"E" is Eastern Time Zone, "C" is Central Time Zone, "M" is Mountain Time Zone, and "P" is Pacific Time Zone. Occasionally, an area code will fall in more than one time zone. In this case, the abbreviation is a combination of the previous abbreviations. Some area codes are shown with time zones referencing Universal Coordinated Time (UTC).
Additional technical status can be retrived from the North American Numbering Plan Administration on the 650 area code specific link here.
Area code 650 went live into service on August 02, 1997.  It was formed as a subdivision of the 415 area code.  It has had the 764 area code(s) overlaid on it.
This area code went live on August 02, 1997 as an "overlay" on the 764 area code. This means the 650 area code was created in part to provide more telephone numbers for people in the 764 area code area. In other words, 650 is a subdivision of the 764 area code. Due to popularity, this area code is starting to run out of free telephone numbers for people to use which means that this area code is technically referred to as being "in jeoparady." Although planning efforts have been put on hold, a notice has been distributed regarding the area code subdivision. 2
SAN MATEO, SSNFRNCSCO, MILLBRAE, WOODSIDE, REDWOOD CY, LOS ALTOS, MT VIEW, PALO ALTO, SNCRL-BLMT, PESCADERO, MOSS BEACH, SNFC JUNPR, HALFMOONBY, PACIFICA, LA HONDA, SNFC CNTRL
Number of major cities served
Names of major cities served (ZIP code)
San Mateo (94403), San Bruno (94066), Millbrae (94030), Menlo Park (94025), W Menlo Park (94025), West Menlo Park (94025), Redwood City (94063), Los Altos (94022), Los Altos Hills (94022), Mountain View (94041), Anaheim (92805), Federal (92805), Palo Alto (94306), Palo Alto (94301), San Carlos (94070), Pescadero (94060), Moss Beach (94038), Half Moon Bay (94019), Princeton By The Sea (94019), Pacifica (94044), Sharp Park (94044), Daly City (94015), Broadmoor Vlg (94015), Burlingame (94010), Hillsborough (94010), La Honda (94020), San Francisco (94143)
36 telephone companies servicing the 650 area code
List of telephone companies
O1 COMMUNICATIONS, INC. - CA, COST PLUS COMMUNICATIONS, LLC - CA, T-MOBILE USA, INC., SPRINT SPECTRUM L.P., NEW CINGULAR WIRELESS PCS, LLC, THE TELEPHONE CONNECTION OF LOS ANGELES, INC., TW TELECOM OF CALIFORNIA LP - CA, LEVEL 3 COMMUNICATIONS, LLC - CA, XO CALIFORNIA, INC., BROADWING COMMUNICATINS. LLC - CA, USA MOBILITY WIRELESS, INC., MPOWER COMMUNICATIONS CORP - CA, MCI WORLDCOM COMMUNICATIONS, INC., CA, CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CA, U.S. TELEPACIFIC CORP. - CA, PACIFIC BELL, GLOBAL CROSSING LOCAL SERVICES, INC.-CA, SOUTHWEST PAGING, NETWORK SERVICES LLC, NEXTEL COMMUNICATIONS, INC., PAC - WEST TELECOMM, INC., COOK TELECOM, INC., AT&T LOCAL, METRO PCS, INC., ASTOUND BROADBAND, LLC - CA, DIGITCOM SERVICES, INC., TELEPORT COMMUNICATIONS GROUP - SAN FRANCISCO, ALLEGIANCE TELECOM, INC. - CA, CREATIVE INTERCONNECT COMMUNICATIONS, LLC - CA, MCIMETRO ACCESS TRANSMISSION SERVICES LLC, CF COMMUNICATIONS, LLC DBA TELEKENEX - CA, YMAX COMMUNICATIONS CORP. - CA, COMCAST PHONE OF CALIFORNIA, LLC - CA, NORTH COUNTY COMMUNICATIONS CORP. - CA, UTILITY TELEPHONE, INC. - CA, BROOKS FIBER COMMUNICATIONS OF CALIFORNIA - CA