The necessity to time measurement came to people in the ancient times. The first calendars appeared thousand years ago during the human civilization. People learned to measure the time intervals and compare them to the repeated events (like day to night change, the phases of the moon and order of the seasons). Without using the units for measuring time people would not be able to live, communicate with each other, making business trading, and work on the lands. Originally, the track of time was primitive, but as the human culture developed and the with human practical requirements increase, the calendars were also developed and gradually such terms as year, month and week appeared.
Long ago every tribe, city and country developed their own calendars arranged in different ways. The lunar, luni-solar and solar calendars appeared. The Sumerians used lunar calendars 2500 BC ago. Chinese and Indians used luni-solar calendars in the ancient times. Today the whole world uses the solar calendar inherited by the ancient Romans.
The calendar is a defined accounting system of long lapses of time. The word “calendar” is derived from the Latin words “caleo” (means “to proclaim”) and “calendarium” (meant “account book”). The term calendae was proclaimed on the first day of the month in the Roman calendar and it was common to pay the interest on debt on that day.
The actual calendar that we use now came from the ancient Romans. The first Roman calendar (that went through in 700 BC) included 10 months. The first month (it was March) was named in honor of Mars, the god of war; the second derived from the word “apricus” meaning “heated by the sun”; the third month was named in honor of Maia, the goddess of growth and the mother of Mercury, the fourth dedicates to Juno goddess, the consort of Jupiter. The fifth and the rest months had numerical Latin signs. This calendar consisted of 304 days. This inconvenience was reformed in 650 BC. Two other months were added to the calendar. The eleventh was named in honor the bifacial god of Janus, while the twelfth, which is February, was derived from the word “Februaries” meaning purification.
The Romans used their original way of counting days and months. The first day was called calends, while the seventh day was called nones, the 15th day (which was a full moon) in long months and 13th day in short months were called ids. The days before calends, nones and ids were called eves. In addition to that, the ancient Romans counted the days backwards and not forwards like we do.