UTC was used beginning in the mid-twentieth century but became the official standard of world time on January 1, 1972. UTC, while based on zero degrees longitude, which passes through the Greenwich Observatory, is based on atomic time and includes leap seconds as they are added to our clock every so often. With this precise accuracy of time, UTC was born. In addition, it became understood that due to the irregularity of the earth and the sun's movements, the exact time needed to be modified occasionally through the use of leap seconds. Atomic clocks did not need to keep time based on average solar time at a particular location because they were very, very accurate.

Because of this - GMT is pretty much an 'average' or an estimated guess as to what time it is where you live.Īs more sophisticated time pieces became available to scientists, the need for a new international time standard became apparent. This observatory broadcasts the current time of the world based on the calculations of where the Earth rotation is in relation to the prime meridian.īecause of the fact that GMT is outdated - it doesn't consider other factors that are important to calculating time - such as where the earth is in relation to the sun.

Windows is always defaulted to use GMT as the location to set the time and date. Every time the other OS boots up - it changes around your BIOS settings in-order to 'correct' the CPU clock timer - which is essential for any computer to calculate things correctly. The simple explanation is Windows uses Greenwhich time, and OSX uses Universal Time. Hope the mods are alright with that, and that this doesn't violate any posting guidelines. I just thought I'd give people an easy to find guide for this information. Building a CustoMac Hackintosh: Buyer's Guide

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