10 months
The Ancient Roman calendar is known as the Calendar of Romulus. The months of the Calendar of Romulus are Martius, Aprilis, Maius, Iunius, Quintilis, Sextilis, September, October, November, and December.
The original Roman calendar, traditionally attributed to Romulus, had ten months, beginning in March and ending in December. These months were followed by a winter period that was not assigned to any month. Later, around 713 BCE, King Numa Pompilius added January and February, making a total of twelve months in the calendar.
The Romans had three calendars over the 1,200 years of their history. Only the first one, the Romulean calendar created by Romulus, Rome's first king, had 10 months and this lasted only for about 40 years. The second king of Rome, Numa Pompilius, reformed the calendar and created one with 12 months (the calendar of Numa). The Julian calendar, created by Julius Caesar, also had 12 months. Caesar also switched from a lunar to a solar calendar.
The very first calendar established by Romulus the founder of Rome and its first king (the calendar of Romulus) only had ten months: March to December (Martius to Decembris). The month was called Decembris because it was the tenth month. The name is derived from decem, the Latin for ten. The second king of Rome, Numa Pomplius, introduced a new calendar (the calendar of Numa) and created twelve months by adding Ianuarius and Ferbuarius (January and February). The year still started in March and December remained the tenth month.
The Chinese lunar calendar does not use months, rather divisions. The Chinese lunar calendar has 24 divisions in a year.
13
3
There are 11 months in a Mayan Calender
The original Roman calendar was said to be invented by Romulus, the first king of Rome, at around 753 BCE (Before Common Era). The calendar started the year in March (Martius) and consisted of 10 months, with 6 months of 30 days and 4 months of 31 days. The winter season was not assigned to any month, so the calendar year only lasted 304 days with 61 days unaccounted for in the winter. The Romulean calendar was short lived. The second king of Rome, Numa Pompilius, reformed the calendar. The Calendar of Numa had twelve month. It had 6 months of 29 days and 6 months of 31 days. it remained a lunar calender.
six months plus one week
12 (twelve).
About five and a half calendar months and almost six lunar months.