These are Western Cultural Generations. Japan and Asia and portions of Europe will have their own generational definitions based on major cultural, political, and economic influences.

Gen Y: “The Millennials” Born between 1980 and 1995The Millennials grew up and began their careers in a time when:

• Almost every home (except 3rd world countries) had an internet connection and a computer
• 2008, the largest economic decline since the great depression
• 911 Terrorist attacks on the World Trade Center and the Pentagon
• The effect of 20+ years of offshoring of American jobs is finally felt
• Enron – energy trading scams and corporate fraud on a national level
• Global warming becoming obvious with unusually severe storms, hotter weather, colder weather, more droughts etc
• President G. W. Bush, Rumsfeld and Dick Cheney deceived the entire nation about weapons of mass destruction and the subsequent invasion and occupation of Iraq
• The explosive growth in online companies such as Google, Facebook, SalesForce.com, LinkedIn, EBay, PayPal
• A revolution in the way we work, including widespread acceptance of flex-time, work from home, freelancing
• The US is divided 50:50 with different and opposite fundamental beliefs and values
• Way too many crazy people are shooting their fellow Americans with weapons of rapid destruction
• Congress becoming dysfunctional
• Housing prices growing beyond most young people’s reach​

Gen X: Born between 1965 and 1979According to WikiPedia, Gen X was originally called “Gen Bust” because their birth rate was vastly smaller than the preceding Baby Boomers.
Gen X’ers were the first generation to experience:

• The highest level of education in the US to date
• The 1976 Arab Oil Debacle and the first gas shortages in the US
• The price of gold soaring to $1000/oz for the first time
• The fall of the Berlin Wall and the splitting apart of the Soviet Union
• MTV and the rise of Disco
• China’s momentary flirtation with personal freedom and the tragedy of Tiananmen Square
• Fighting in the first Gulf War
• NAFTA where President Bill Clinton paves the way to give away millions of American jobs

Baby Boomers: Born between 1946 and 1964Baby Boomers are defined as being from the huge population increase that followed World War II, and the Great Depression.
They grew up in a time of prosperity and an absence of world wars. They were the Flower Children, taking LSD and protesting the war in Vietnam.
Unlike their parents who grew up during the Great Depression, Boomers became the great consumers. They became famous for spending every dollar they earned.
This was the first Western Generation to grow up with two cars in every garage and a chicken in every pot.
Baby Boomer spending and consumerism has fueled the world economies.
The Baby Boomers fought for environmental protection.
Baby Boomers were the first generation to experience:

• A time of unparalleled national optimism and prosperity
• The Cold War, fear of a nuclear attack from Russia, bomb shelters and hiding under a desk at school
• The assassination of President John F. Kennedy
• The assassination of Martin Luther King
• The confidence building from putting a man on the moon
• The incredible waste and destruction of the War in Vietnam
• The Civil Rights Movement

The Silent Generation: Born between 1925 and 1945Those of the Silent Generation were born during the Great Depression. Their parents were mostly of the Lost Generation.
They grew up expecting a hard life. This was the era when a Christmas present might be a orange or a full meal.
They are called the Silent Generation because as a group they were not loud. They did not protest in Washington. There were no major wars to protest.

The Greatest Generation: Born between 1910 and 1924Those of the Greatest Generation grew up during the Great Depression and probably fought in World War II. They are also known as the GI Joe Generation.
They are the parents of the Baby Boomers.
They were named the Greatest Generation by Tom Brokaw, famous News Broadcaster. Brokaw said they were the greatest because they fought for what was right rather than fighting for selfish reasons.
They certainly made great self sacrifices, fighting to protect people in other countries from the likes of Hitler, Mussolini and Japanese Kamikaze suicide bombers.
Makes one wonder what they will call those bankers and insurance company executives who fought only for personal gain thus creating the 2007-2009 financial collapse.

Primary Sources for our Data on Generations:

• WikiPedia
• The Lost Generation
• The Interbellum Generation
• The Greatest Generation
• The Silent Generation
• The Baby Boom Generation
• Gen X
• Gen Y
• Gen Z
• US Census Bureau
• Harvard
• Pew Research

Why the Overlap in Dating Generations?In the USA, there are two different methods for marking the borders between generations.
The US Census Bureau appears to use census data (duh) and the rise and fall of the birth rate to mark borders between generations.
Other researchers, such as Pew, use major cultural events to define the borders between generations.
Here is an example of using the birth rate fluctuations to define borders between generations:
What Generation Are You If You Are On The Cusp?If your birth date falls on the border between two generations, which one do you pick?
Pick the generation that you relate to the most, and the one you want to be part of.
Why so arbitrary? This is not a precise science with firm definitions.
Updates and RevisionsOn 9-29-2016 we made the following adjustments to the date ranges of Gen x, Millenials, Gen Z:

• Changed Gen X last births date from 1981 to 1979
• Changed Millennial start birth date from 1975 to 1980
• Changed Gen Z start birth date from 1995 to 1996
• Changed Gen Z last births date from 2015 to 2010

On 11-9-2016 we made these changes, based on further research:

• Changed Silent Generation start from 1923 to 1925 and end from 1944 to 1945 based on more research
• Changed the end of births for the greatest generation from 1925 to 1924 – for the convenience of having less overlap
• Changed Gen X start from 1961 to 1965 – and end back to 1979 – based on more research and to be consistent with Pew

Why make these changes? The cut off dates for each generation vary over time as the characteristics of that generation become more well understood. In the US, it appears demographers are trying to stick to ranges of 15 years (Japan uses 10 years). Finally, as the public pays more attention to generations, such as Millenials, certain dates become more accepted.
The bottom line is that the experts do not agree on when generations begin and end. Sorry for this confusion. I would prefer to have things nice and tidy, precise and exact.