What is lustrum?

What Does lustrum Mean

A half decade is a temporary period of five years . The term comes from the Latin word lustrum and is linked to lustratio , a ceremony that took place every five years in Ancient Rome and Ancient Greece .

The lustratio implied a purification . In the case of the Romans, it was sought to guarantee divine protection through various rituals that allowed to purify the herds, the lands and even the army. Attendance at the event was mandatory for all citizens. For the Greeks, the lustratio allowed to reverse the disgrace that weighed on some city or person.
With the advancement of history , lustratio ceased to exist, although its periodicity ended up giving rise to the concept of lustrum. Thus, nowadays any period that extends for half a decade is referred to in this way .

Five years, therefore, is equivalent to sixty months . Its beginning may or may not coincide with the beginning of a year : the important thing is that the stage extends over five years.
Suppose the government of a nation decides to build a new hospital. The works begin in March 2013 and end in March 2018 ; that is, five years later. It can be said, in this way, that the construction of the health center took five years.
Take the case of a famous actor who lived outside their country between 1980 and 1985 . When reviewing his life in an interview, he comments that he lived abroad for five years, referring to the five years he spent away from his homeland.
It is important to note that the five-year concept can be used with a certain degree of imprecision if the exact duration of an event is not so relevant. In other words, not whenever we hear this term in a sentence it is translated as exactly five years, with each and every one of its days.
A possible explanation for this concession is that the years of our calendar (that is, in the Gregorian) do not always last the same: let's not forget that the leap year, the one that occurs every four, has one day more than the rest. This correction is carried out to compensate for the lag between the tropical year and the calendar.
Here we enter even more technical terrain. The time required for the mean length of the Sun to increase by 360 at the ecliptic is called a tropical year or a tropic year , that is, for it to complete one revolution. This lasts 365.242189 days if calculated in mean solar time. The calendar year, on the other hand, is simply 365 days long, and this generates the aforementioned lag .

Taking all this into account, we could say that five years should always include four years of 365 days and one of 366 days, since in the Gregorian calendar there are no periods of five years that do not include a leap year . However, in everyday speech and even in areas of a certain level of precision, it is common for this concept to be used to describe a period that begins and ends in the same month, approximately five years apart.
There are other terms that serve to express groups of years, and that are complementary to "five years." To speak of two, ten, one hundred and one thousand years we can use biennium, decade, century and millennium , respectively. Again, it is not common for them to be used strictly, but we usually round the number of months and days. In addition, a biennium can consist of two 365-day years, but it can also include a leap year. In the case of the decade, there should always be two leaps.

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