| The gregorian calendar also known as the western or christian calendar is the most widely used calendar in the world today its predecessor the julian calendar was replaced because it did not properly reflect the actual time it takes the earth to circle once around the sun known as a tropical year | |
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| The adoption of the gregorian calendar was an event in the modern history of most cultures and societies marking a change from their traditional or old style dating system to the modern or new style dating system that is widely used around the world today some states adopted the new calendar from 1582 some did not do so before the early twentieth century and others did so at various |
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