California is further south than London. Since it's summer in the Southern hemisphere, the days are longer there. The further South you go, the longer the days are, because you're closer to where the sun is directly overhead.

Conversely, if you were at the geographical North Pole right now, you would have zero daylight all day, as they are so far North that the sun doesn't come up over the horizon. They have a several-month-long night.