The adoption of the Gregorian calendar by Great Britain and its overseas possessions marked a pivotal moment in the synchronization of timekeeping practices across Europe. Previously, the Julian calendar, instituted by Julius Caesar in 46 BC, had provided a system that, while effective for many centuries, had become increasingly inaccurate by the 16th century due to its miscalculation of the solar year. The Gregorian calendar, introduced by Pope Gregory XIII in 1582, corrected this error by adjusting the leap year system, thus restoring the calendar's alignment with the equinoxes and solstices.

When Great Britain enacted this change, it involved skipping 11 days in the calendar – September 2 was directly followed by September 14, a move that caused significant confusion and discontent among the populace. Many people viewed the lost days with suspicion, and there were protests, with some believing they had been cheated out of time. The implementation of the Gregorian calendar not only standardized the date used by Britain and its colonies but also facilitated trade, communication, and scientific endeavors by eliminating discrepancies in timekeeping across different regions.

This transition reflected a broader acceptance of scientific approaches to time and, by extension, the increased influence of Enlightenment thinking. The adoption was not without resistance, yet it cemented the Gregorian calendar as the international standard for civil use, leading to its eventual global implementation as nations recognized the practical benefits of uniform timekeeping.