Daylight saving time changes in California, United States

California uses the IANA time zone identifier America/Los_Angeles. The current local offset is UTC-7 / PDT.

Best Time to Call California

Business hours in California (9 AM-5 PM local time) fall at these local times elsewhere:

• Sao Paulo: 1:00 PM - 9:00 PM ( Partial overlap)
• Frankfurt: 6:00 PM - 2:00 AM (next day) ( Partial overlap)
• Johannesburg: 6:00 PM - 2:00 AM (next day) ( Partial overlap)
• Singapore: 12:00 AM (next day) - 8:00 AM (next day) ( Outside normal hours)
• Hong Kong: 12:00 AM (next day) - 8:00 AM (next day) ( Outside normal hours)
• Istanbul: 7:00 PM - 3:00 AM (next day) ( Partial overlap)
• Auckland: 5:00 AM (next day) - 1:00 PM (next day) ( Outside normal hours)

Times shown reflect current UTC offsets and may shift by up to an hour around daylight saving transitions.

Current Time in Cities of California, United States

About Time in California

The Business of Time at Lick Observatory

High above San Jose on the summit of Mount Hamilton sits Lick Observatory, completed in 1888 and recognized as the world's first permanently staffed mountaintop observatory. It was funded by a $700,000 bequest from James Lick, a self-made real estate fortune builder who had arrived in San Francisco in 1847 and later chose the mountain as the site for his memorial, asking to be buried beneath the future telescope's foundation. Reaching the summit required blasting a new road through solid rock, a project that removed more than 40,000 tons of stone and took until 1877 to finish, years before the observatory itself was done. For its first several decades, Lick housed the largest refracting telescope in the world, at 36 inches, and its astronomers used it to identify Amalthea, the fifth moon of Jupiter, in 1892, the first new Jovian moon found since Galileo's original discoveries nearly three centuries earlier.

What is less well known is that Lick Observatory was also, from its earliest years, a working commercial operation whose main paying customer was the concept of accurate time itself. Its own official handbook stated plainly that the one point where a major observatory's work touched the direct business interests of ordinary communities was the distribution of time by electric signal, sold to railroad and telegraph companies, city and tower clocks, and private firms who needed a dependable standard to set their own instruments by. Starting in the 1880s, Lick transmitted telegraphic time signals at noon each day except Sundays and holidays, a service that continued into the twentieth century and helped California railroads and businesses stay synchronized in an era before any centralized national time authority existed. In this sense, the astronomers on Mount Hamilton were doing double duty: charting the heavens at night, and quietly keeping California running on schedule by day.

California and the Ballot Box: Deciding Daylight Saving Twice

Unlike most states, where daylight saving time has always been a matter for the legislature, California voters have twice been asked to decide the question directly, seven decades apart. Daylight saving was first imposed nationally as a wartime energy measure and then left to individual states once the war ended. In 1949, California voters approved Proposition 12, a ballot initiative that permanently established seasonal daylight saving time in the state. Because the practice had been created by a vote of the people rather than an ordinary act of the legislature, any future change to it legally required another vote of the people, not simply a new law.

That second vote came in November 2018, when California placed Proposition 7 before its citizens. The measure did not itself create year round daylight saving time; instead it repealed the 1949 initiative's lock on the system and gave the state legislature the power to change the daylight saving period by a two thirds vote, provided any change complied with federal law. Voters approved it decisively, with 59.75 percent in favor on a turnout of nearly 12 million ballots cast. Assemblymember Kansen Chu, who had championed the measure, followed up in 2019 with Assembly Bill 7, an attempt to formally establish year round daylight saving time pending federal authorization, but the bill stalled in committee and died in 2020. As a result, California remains on the same seasonal schedule it has followed since 1949, still legally free to change only if both Sacramento and Washington eventually agree to act.

Santa Clara and the Cesium Clock

Long before Silicon Valley became synonymous with computing, one of its founding companies was quietly redefining how the world measured time itself. In 1964, Hewlett Packard's Santa Clara facility introduced the model 5060A, the first cesium beam atomic clock built entirely from solid state components rather than the bulky, fragile vacuum tubes used in earlier atomic timekeeping devices. The shift made precise atomic timekeeping portable and reliable for the first time, and the technology descended from that original Santa Clara design came to underpin an enormous share of the world's standardized timekeeping in the decades that followed; by one estimate, roughly 80 percent of global timekeeping infrastructure by 2007 traced its lineage back to the 5060A and its successors.

The Santa Clara plant did not just build the clocks, it also used them, serving for years as an official timekeeping station for the United States Naval Observatory and maintaining the West Coast reference point for coordinated time. Engineers there ran a program nicknamed the Flying Clock, in which technicians physically carried an operating cesium standard, along with a heavy rechargeable battery pack, on commercial flights to synchronize military timing stations across the Pacific, checking the clock's accuracy against the Naval Observatory both before and after each trip. The same Santa Clara built instruments were later used in scientific experiments during the 1970s that placed atomic clocks at different altitudes to test Einstein's prediction that gravity itself affects the passage of time, confirming that a clock closer to the ground runs measurably slower than one placed higher up, a finding that would have been impossible to verify without the portability the Santa Clara engineers had built into their design.

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