How long is a decade and a century?
a decade is measure of 10 years
a century is a measure of 100 years
you also got a lustrum, a measure of 5 years
and a ‘jubilee’ is 50 years
and a score is 20 years
the 2 weirdos is
(1) a generation, which is the amount of time it takes to replace yourself in the great scheme of things, and by the time most folks is 25 years old, they’ve already managed to produce at least one unit that’ll survive to ‘take over the family business’ by the time THAT one jumps the ‘generation gap’ of ITS ’25 years’.
(2) a lifetime which has been established as ‘3 score and 10’, (3x20)+10, 60+10=70 years of ‘useful productivity’ ‘mean time before failure’, which, in more than 6000 years of development, is STILL valid when you use the same baseline, as are the NOTEWORTHY clusters and individuals that make it beyond the century mark.
It all depends on the calendar that we choose to use.
There are societies that use the Gregorian (majority) and others that use the Julian calendar.
There are also others that use the 13 moon calendar.
All these calendars will create a difference in when months end and begin.
In Russia for example, it is not Christmas until January 7th when the rest of the world has already marked Christmas. This is because of the Julian calendar that the faithful there use. Faithful means Catholics.
So is it always a fact that a decade has 10 years and a century 100 year