Saturday the 18th is the anniversary of the great San Francisco earthquake of 1906. I point this out on Friday in case you want to be awake at the time it happened, which was 5:12 am local time. Now I know for sure that we didn't use Daylight Saving time in 1906, so when the mayor leads a crowd in observance of the quake at Lotta's Fountain
at 5:12 tomorrow morning, they will all be an hour early. The earthquake struck 15 minutes before sunrise as dawn was breaking, not in the dark of night.
Fortunately the United States adopted time zones very close to today's in 1883, when the railroads came up with the idea. Figuring this out for the 1868 San Francisco earthquake would be quite a different task, because then every city kept its own time.
About the 1906 earthquake
Surviving landmarks from the 1906 earthquake
About the San Andreas fault