It's even broader than that. Different sources and countries use different ranges, so where you fall depends on which you consult (some use 1976 as a starting year, others use 1978, and still others use 1980 or 1981.) Some also carve out additional generations (MTV generation / Doom Generation / XY Cusp Generation along with Echo Boomers / Generation McGuire) for people born in the edge years. Here's more:

http://www.esds1.pt/site/images/stories/isacosta/secondary_p...

http://www.boston.com/bostonglobe/ideas/brainiac/2008/04/fin...

The old Wikipedia article on XY Cusp before it got edited: https://en.wikipedia.org/wiki/User:JCDenton2052/mh5

Excerpt: "The XY Cusp includes those people born in the mid-to-late 1970s and early 1980s. The word XY is used because their generational identity is mixed, uncertain, or deviant from X or Y or both, but do not constitute a separate generational group in themselves. Some place the years between: 1976-1983 [3] [4][5] [6] People born within this group are in parallel situations with people born in between previous generations: Generation Jones between Boomer and X - late 50s, early 60s, (teens of the 70s); between Silents and Boomers - late 30s, early 40s (teens of the 50s); and the Beat generation between G.I. and Silents - late 10s, early 20s (teens of the 30s). They are referred to as Cusper Groups, Transitional Times, or Buffer Zones. John Losey states "If you couldn't neatly place yourself in any of the [generations], then you're probably a Cusper. 1943-1947, 1962-1967 and 1976-1983 are each considered transition times. Many people born during these cusp periods identify with the generations on either side."

There's definitely no single standard in sociology on this.