The time differences between Beijing (capital of China) and California's major cities is shown as thus from the current time/date:
09:42 p.m. Tuesday February 23, 2010 in US/Pacific converts to1:42 p.m.* Wednesday February 24, 2010 in Asia/Beijing = 16 hours.
http://www.worldatlas.com/aatlas/infopage/timezonz.htm (there is a world map shown with the time zones. How to figure them is below it, including info on Daylight Saving Time). Or, as I was taught in my Geography major classes, time changes 1 hour for each 15 degrees of LONGITUDE (numbered from 0 in GREENWICH, ENGLAND* to 180 degrees--INTERNATIONAL DATE LINE--east or west. Like so:
W 180** | 165 |150|135|120|105|90|75|60|45|30|15|0*
(all on one line of course. Lines on a sheet of notebook paper work great for this)
**--International date line.
You GAIN an hour going EAST (so the further you go east, you eventually GAIN a day) and you LOSE and hour going WEST (eventually LOSE a day). An easy way to do this is to make a line like above, find the nearest longitude of the city you want to know about--longitude lines on maps run top to bottom or north to south--and the city where you are, and count from one to the other. For instance, if a city is at 147 degrees west longitude, you'd go by the 150 line to the LEFT of the 0 because it's closest to that than to 135; and the other city is at 62 east longitude, you'd go by the 60 degree line to the RIGHT of the 0 and count how many lines are between them. The 150-135 west is 1, etc. and to the 60 on the right (east) is a total of 14 lines. So, there are 14 hours between them. For example, if it is 2 a.m. at 147 degrees West longitude, 14 hours AHEAD would be 4 p.m. East longitude.
Hope that wasn't hard to understand. =)
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them