Join Date: Nov 2007
Location: SF Bay area
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As with so many questions, the answer is, "It depends."
The extra factor here is the Equation of Time, which is the difference between apparent solar time (what a sundial tells you) and mean solar time (what a sundial would tell you if the sun moved at a constant rate across the sky every day over the course of a year).
If the equation of time is zero, then local apparent solar time is equal to local standard zone time at the standard meridian for that zone. The prime meridian and every 15 degrees of longitude east and west of the prime meridian are standard meridians for the corresponding time zone.
So towards the end of December when the equation of time is zero, and we're not on daylight savings time (the navigator's bane), then at 120 W longitude (the standard meridian in my time zone), it will be local apparent noon when my clock says 12:00.
s/v Laelia - 1978 Pearson 365 ketch