time zone changed

I just discovered that my clock is showing London, England time. I tried to configure the time zone, but it is already set to Pacific Std Time. Why did this happen? How do I fix it? How do I keep it from happening again? -- John R. Sowden AMERICAN SENTRY SYSTEMS, INC. Residential & Commercial Alarm Service UL Listed Central Station Serving the San Francisco Bay Area Since 1967 mail@americansentry.net www.americansentry.net