Rome initially had a lunar calendar, which consisted of twelve months based on the moon’s cycle. Because a lunar month varies between twenty-nine and thirty days, the year was around 355 days long. To adjust for the discrepancy in the matching of months and seasons (which are based on the movement of the earth around the sun) the Romans added an extra month of twenty-two days after a certain number of lunar years.

The fact that the solar year lasted 365.25 days was known as early as the third century BCE, but it was only in 46 BCE that Julius Caesar adopted this year length by ordering that years shall be 365 days long and an extra day shall be added to every fourth year. In fact, to make up for missed days in past years (which had led to discrepancies in the timing of seasons in the calendar) Caesar ordered that the year before the inception of the new calendar would last 445 days! The Julian calendar was soon adopted by the rest of Europe. This is the system we use today, with minor modifications, as the Gregorian calendar (after Pope Gregory XIII who, in 1582, decreed that the last year of every century shall only be a leap if it was exactly divisible by 400). The origins of the names for days of the week are also Roman; in English we use the Saxon forms of the Latin names for the seven heavenly bodies.

The Romans borrowed the knowledge of sundials from the Egyptians and Greeks, and developed it into the form which was used since then and can still be seen today. They also developed smaller versions that could be carried around while travelling.¹ Like the Greeks, the Romans also used water clocks to measure the passage of time. In this field, there was little innovation in Rome; however, the Romans found more uses for the clock and made it more widespread. In Roman courts, a vessel from which water dripped steadily was used to regulate the time each speaker was given. Clocks were also used to keep time in chariot races.