Lustra to Months (lustrum to mo)

1 lustrum equals 60 months exactly.

1 lustrum = 60 months

How to convert lustra to months

To convert lustra to months, multiply the number of lustra by 60. This factor is exact. To go the other way, multiply months by 0.01666666667 (rounded).

months = lustra × 60

Example: 10 lustra = 600 months.

Months and years are not constant. This site uses the average Gregorian year of 365.2425 days, so one 'year' converts to 365.2425 days, not 365; use 'common year' for exactly 365 days.

About these units

Lustrum (lustrum)

Ancient RomanHistorical unit (no longer in standard use)

Five years, the interval between Roman censuses and the ritual purification that closed each one.

Roman censors counted citizens and their property about every five years, and the period between counts took the name lustrum. The word is tied to a Latin verb for purifying, because each census ended with a solemn purification of the people, often performed through the sacrifice of a bull, a ram and a pig in the Campus Martius. Ancient tradition credited the first one to King Servius Tullius in 566 BC.

Censors held office from 443 BC, and a later law cut their term from a full lustrum to 18 months. The interval was not always kept: Livy recorded only 21 lustra between 443 BC and 294 BC where 30 might have been expected, and some censuses took place without the ritual. The last censors were appointed in 23 BC under Augustus. In modern English the word survives for any five-year span. Using a Gregorian year of 365.2425 days, one lustrum is about 157.8 million seconds, which is the figure used here.

1 lustrum = 157,784,760 seconds (exactly).

Sources: Wikipedia: Lustrum; Wikipedia: Roman census

Month (mo)

CalendarCurrent unit

One twelfth of an average Gregorian year: 30.436875 days. Calendar months actually range from 28 to 31 days.

Month and Moon are cognates, and the unit began as the Moon's cycle of phases, about 29.53 days from one new moon to the next. The trouble is that 12 of these fall short of a solar year, so calendars have had to choose. The Islamic calendar stays purely lunar, so its year is about 11 days shorter than the solar year, while the Hebrew calendar is lunisolar, using a 19-year cycle with an extra month. Even the start of a lunar month is still debated between observing the crescent and calculating it.

Gregorian months are a compromise that drifted far from the Moon. Their lengths run from 28 to 31 days, and this site uses their mean of 30.436875 days, one twelfth of the average year. The names also keep Roman history: September to December preserve the Latin numerals for seven to ten, since they were originally the seventh to tenth months, and Quintilis and Sextilis were renamed for Julius Caesar and Augustus. When a contract says month, check whether it means a calendar month or thirty days.

1 month = 2,629,746 seconds (exactly).

Sources: Wikipedia: Month; Wikipedia: Lunar calendar

Related conversions

See all time units.