How do you refer to decades (such as the '70s) in Spanish?

Question: How do you refer to decades (such as the '70s) in Spanish?

Answer: The most common way to refer to "the '70s" would be los años 70 or los años setenta. Note than when the decade is written numerically, most writers do not precede it by an apostrophe as is usually done in English. The 70 form and the setenta form appear to be used about equally, although the spelled-out version is more common in formal writing.

It is also fairly common to use a longer form, la década de los setenta, which again is somewhat formal. The longer form also would normally be used when the century isn't clear from the context, as in la década de 1870 or, less commonly, la década de los 1870. The form la década de los 1870s (note the s after the year) is very seldom used.

It is possible to use phrases such as los setentas or los cincuentas alone to refer to the '70s and '50s, but it is probably not best to use that form unless you hear it being used by native speakers, since they can sound like an anglicism.

The word decenio is also used as a translation for "decade." Thus it is possible to say el decenio de los setenta or el decenio de 1970. Again, though, decenio is more formal or literary than década.