I do not do as much conference calls as before, and I don’t use an advanced scheduling system called Microsoft Outlook (TM), so I often mass meetings up. After booking three meetings wrong, I decided to really look into the details of how time zone, daylight saving works.

Converting San Francisco Time to Beijing Time

Although there are many tools doing the conversation, I found many tools converted the time wrong, since the new change of the Energy Policy Act of 2005 in US extended one month of daylight saving

locks were set ahead one hour on the second Sunday of March (March 11, 2007) instead of on the first Sunday of April (April 1, 2007). Clocks were set back one hour on the first Sunday in November (November 4, 2007), rather than on the last Sunday of October (October 28, 2007).

— Wikipedia contributors, ‘Energy Policy Act of 2005’, Wikipedia, The Free Encyclopedia, 16 June 2009, 01:21 UTC, <http://en.wikipedia.org/w/index.php?title=Energy_Policy_Act_of_2005&oldid=296664740> [accessed 16 June 2009]

That means, pay attending to the change from March to November.

When it is hot (summer time), the difference between Beijing and San Francisco is becoming less (from formal 16 hours to 15 hours).

The strict way to do the calculation is, always add 15 hours in summer time or 16 hours in winter time to San Francisco time to get the right Beijing time.

For example, a meeting starts at 7:00 PM, June 20, 2009 = 10 AM, June 21, 2009 – my most preferred time to call.

A easier way is to flip the AM and PM, and advance by 3 hours in hot time, and 4 hours in cold time.

Beijing Time to US Time

The way to calculate it is also easy: flip the AM and PM, and backward 3 hours (in hot time), or 4 hours (in cold time).

Hope I can always do the calculation right.

What time is it now? 22:43:37, June 23, 2009 – that is 7:43:37, June 23, 2009 in US.

P.S. China adopted Day Time Saving, but abandoned the practice.