An Etymological Dictionary of Astronomy and Astrophysics
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Any of several → lunar calendars used by Romans before the advent of the → Julian calendar in 46 B.C. The original Roman calendar, which had 10 months and 304 days, went back to the Greek calendar, although Romulas, the ruler of Rome, is given credit for starting the Roman calendar. Originally, the Roman calendar started the year in March with the → vernal equinox. The Roman calendar went through several changes from 800 B.C. to the Julian calendar. The 800 B.C. calendar had 10 months and a winter period, with a year of 304 days. In this calendar, the first month, March, was followed by Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, December, and Winter. The months starting with and following Quintilis all used the Latin numbers for names. Finally, for political reasons, the Romans made a change around 150 B.C. when they started using January as the beginning of their calendar year. Around 700 B.C. the 304 day calendar was expanded to 355 days by adding the months of February and January to the end of the year. Later in 450 B.C., January was moved in front of February. Finally, in 150 B.C. the Romans began to use January as the beginning of the calendar year. This calendar was replaced by the Julian calendar in 46 B.C.

From L. Romanus "of Rome, Roman," from Roma "Rome," of uncertain origin.

A calendar based on the apparent yearly motion of the Sun on the → celestial sphere. The year is usually reckoned with respect to the → vernal equinox, approximately for example in the case of the → Gregorian calendar and accurately in the case of the → Iranian calendar.

→ solar; → calendar.

A → lunisolar calendar used now in Vietnam mainly for determining seasonal holidays and cultural events. It is in fact the → Chinese calendar computed for Hanoi. It has 12 months of 29 or 30 days each (→ synodic month) and the year totals 355 days. The → lunar year is therefore 11 days shorter than its solar counterpart. To keep up with the solar pace, every 19 years seven extra months are added to the calendar. In practice, approximately every third year an → embolismic month is included. The New Year, called Tet, begins at the second → new moon after the → winter solstice. The Vietnamese calendar has some minor differences with the Chinese calendar. For example, it uses the cat and buffalo instead of the Chinese rabbit and cow respectively in the → zodiac.

From Vietnam "Viets of the South," from Viet the people's name + nam "south;" → lunar; → calendar.