Just so people are clear, the term Millennial is the new word for Generation Y. I never knew I was a millennial until I researched the word 
. If you were born in the early 1980’s you can choose Generation X or Y (so whether to be a millennial or not) as there is no precise cut off year.
Google defines it as:
a person reaching young adulthood in the early 21st century.
Wikipedia defines it as:
Millennials, also known as Generation Y or Gen Y , are the generational demographic cohort following Generation X. There are no precise dates for when this cohort starts or ends; demographers and researchers typically use the early 1980s as starting birth years and the mid-1990s to early 2000s as ending birth years.
The other Generations for reference according to Wikipedia:
Generation X or Gen X is the demographic cohort following the baby boomers and preceding the Millennials. There are no precise dates for when Generation X starts or ends. Demographers and researchers typically use birth years ranging from the early-to-mid 1960s to the early 1980s.
Generation Z or Gen Z (also known as the iGeneration, Homeland Generation, Centennials, Generation Sensible, and Post-Millennials) is the demographic cohort after the Millennials (Generation Y). […] There are no precise dates for when this cohort starts or ends, but demographers and researchers typically use the mid-1990s to mid-2000s as starting birth years. At the present time, there is little consensus regarding ending birth years.