nián dài
a decade of a century (e.g. the Sixties)
age
era
period
CL:個|个[ge4]
nián dài chū
beginning of an age
beginning of a decade
nián dài xué
chronology (the science of determining the dates of past events)
dōu shén me nián dài le
What decade are you living in?
That's so out-of-date!