
Originally Posted by
AZBuck
... but the consequences of ignoring it can be huge. Consider the Austrian and Russian offensive against France in the Napoleonic Wars. The Austrians used the Gregorian Calendar while the Russians used the older Julian Calendar. The two calendars differed in how they accounted for leap years and had been slowly drifting apart since the 16th century. When the Austrians showed up for battle at Austerlitz on Sept. 26, 1805, they expected the Russians to join them. The Russians showed up 12 days later when their calendar said it was the 26th. Napoleon won.