While no year has 2 decades between years, perhaps you mean what years signal a decade has passed. Years ending by counts of 10, so...
So if you wanted to show 2 decades with the above decades, it would be written as:
7 decades which is 70 years
1958
well a decade is 10 year so 2 decades will be 20 years
1 year is greater then 350 days
2 decades after 1620 is 1600 because 1 decade is 10 years so 2 decades must be 20 so 1620 + 20= 1640
21 decades after 2017 will be 2227.
1913 - 120 = 1793
A decade is 10 years. Since there are 20 years from 1942 to 1962, that would be 2 decades.
Two decades before 1972 is 1952. A decade is ten years, so two decades would be twenty years. Subtracting twenty years from 1972 gives you 1952.
1793, as it was 120 years before 1913.
If one year has 12 months, then a decade would have 120. And two decades would be the double of that, so 240
The main one was in 1845-1851 but it continued for decades afterwards