Diamond Bar, California
Pacific Time Zone (UTC-8) · CA · —
909
1992
San Bernardino
California
Pacific
Split
+1
840
2021
San Bernardino
California
Pacific
Overlay
About Area Codes in Diamond Bar, California
Diamond Bar, California is served by 2 area codes: 909, 840. When multiple area codes serve the same geographic area, it typically indicates overlay codes have been added to accommodate growing demand for phone numbers. All local calls within Diamond Bar require 10-digit dialing. The city is in the Pacific time zone (UTC-8).
Other cities in area code 909
Frequently Asked Questions
What area code is Diamond Bar, California?
Diamond Bar, California uses area codes 909 and 840.
What time zone is Diamond Bar in?
Diamond Bar is in the Pacific time zone (UTC-8).
Do I need to dial 10 digits when calling Diamond Bar?
Yes, all local calls in Diamond Bar require 10-digit dialing because the area is served by multiple overlay area codes.
When was area code 909 created?
Area code 909 was established in 1992 as a geographic split from a larger area code region to serve the growing population.
What cities share area code 909 with Diamond Bar?
Other cities sharing area code 909 with Diamond Bar include Chino, Chino Hills, Claremont, Colton, Fontana, among others.
Diamond Bar, CA · Pacific Time Zone