Every 10 years.
Well unless it's a trick question I would have thought at 00.01 on the 1st of January of the current set of 10 years.
For example
00.01 01/01/2010
00.01 01/01/2020
00.01 01/01/2030
etc
1990s
Decade.
the 1960's
In the last decade there was terror in the west. The 1940s DECADE experienced World War, V-J Day and the start of the Cold War.
According to the calendar, because there is no "0" year, the new decade just started January 1, 2011. Common use of the word decade, because we refer to the decade of the 80's or 90's, the new decade starts on January 1 of the decade that is being referred to. This is because it is illogical to say the decade of the 80's doesn't include 1980 but does include 1990. So, if you like the common use of the word decade, instead of the calendar use, the new decade will start on January 1, 2020.
The first episode was in October 1963.
1900.
1960
It started in 2010.
It started around 1963.
Decade, Decagon and Decatron
that's immposible to answer