In generational astrology, the sign Neptune is in represents the image and culture of the age group. This also means that the sign Neptune is in is the image and culture of the time period, as everyone born is "trapped" with the astrological weather of the time they were born for the rest of their life, and with the outer planets, generations are basically "torchbearers" for the time period they grew up in, which is why people tend to be nostalgic for their childhood years, as Pluto and Neptune stay in the same sign for years after a person is born unless they're at the tail end of a generation. Because of this, Neptune's influence is very significant, despite it not being as personal as the Sun, Moon, ascendant, or inner planets.
Neptune in Leo (1914-1929)
This was the Roaring Twenties, as the culture of these years was based on celebrities, movies, jazz music, and extroversion in general after the invention of the telephone and automobile. As a result, the children born during this era have a warmth and thirst for the "good life" that the generation after them didn't (also with Pluto in Cancer).
Neptune in Virgo (1928-1943)
This was the Great Depression and WWII. The culture in this era basically WAS the Depression, as people just wanted a job and a roof over their head, which many didn't have then. The children born during this era are more serious than the Neptune in Leo Pluto Cancers, as Neptune in Virgo was a more serious era in general.
Neptune in Libra (1942-1957)
The postwar era. These years were known for classical music (Frank Sinatra, Nat King Cole, Bing Crosby), postwar prosperity, conforming to social norms (one of the shadow sides of Libra is vanity and wanting to fit in, which is why many Baby Boomers and Gen Xers come off as vain as they have Neptune and Pluto in Libra respectively), and overall peace after the Depression and WWII. As a result, the children born during this era are known as the "flower children" and made up the majority of the Vietnam War protesters, as their desire for peace along with their Pluto Leo pride led to the Hippie movement.
Neptune in Scorpio (1955-1970)
The Sex, Drugs, and Rock n' Roll era. These years were when the Neptune in Libras became teenagers and young adults, and became rebellious in a way that the previous generations weren't. The Hippie movement, Vietnam protests, Summer of Love, and Woodstock all took place during Neptune in Scorpio, as well as the JFK and MLK assassinations (Scorpio rules violence and secrets). This era was dominated by classic rock, and the main acts during this era, The Beatles, Rolling Stones, The Who, Jimi Hendrix, Janis Joplin, and The Doors to name a few, were a big part of the Sex, Drugs, and Rock n' Roll culture. Motown, girl groups, rockabilly, and Doo Wop were also big during this time, but more in tune with Pluto in Virgo. As a result of the cynicism of this era, the children born in this era are very cynical in nature (like the Pluto Scorpios in the mid 80s-mid 90s), and are the first "tattoo generation" (the other Scorpio generations, Uranus in Scorpio from 1974-1981 and Pluto in Scorpio from 1983-1995, are also heavily tattooed).
Neptune in Sagittarius (1970-1984)
After the cynical 60s, the Neptune in Sagittarius 70s and early 80s was way more vibrant. This was the era of disco, arena rock, and new wave music, all of which had more vibrant and unique sounds than that of the 60s. Bands that were active in the 60s, like the Rolling Stones and The Who, changed their sound to a more 70s style sound, and the lyrics to the songs had more to do with love and relationships (Libra, as the artists that were big during Neptune in Sagittarius had Neptune in Libra and Pluto was also in Libra at the same time as Neptune in Sagittarius) than sex and drugs (Scorpio). Also prevalent during this era was the rise of religious fundamentalism, as a response to Roe vs. Wade and the previous Hippie culture. As a result, the children born during this era tend to be very jovial and vibrant, and the conservatives born during this era tend to be extreme religious fundamentalists.
Neptune in Capricorn (1984-1998)
The materialism culture. As a member of this generation, I was subject to the idea that the goal (Capricorn) in life was to be what you want to be in order to get a lot of money in order to buy material possessions. In the early-mid 90s, some of the most well known commercials were the Sally Struthers ICS commercials, which were Neptune in Capricorn at its most in your face (they're on YouTube if you haven't experienced them). The music associated with Neptune in Capricorn tended to be more slower than the previous era, as soft rock and easy listening music became dominant (Madonna, Michael Jackson, Prince, George Michael, Whitney Houston, Celine Dion, Mariah Carey, Gloria Estefan, etc.), as well as heavy metal, rap, grunge, and hair bands, which were more in tune with Pluto in Scorpio. Also playing a big part of Neptune in Capricorn was the family TV boom, as numerous sitcoms (Fresh Prince, Roseanne, Family Matters, Full House, Cosby Show, Married With Children, Home Improvement, Seinfeld, Saved By The Bell, Cheers, Different World, Friends, Boy Meets World, Step By Step, Wonder Years, etc.) and cartoons (Doug, Rugrats, Rocko's Modern Life, Ren and Stimpy, Aaahh! Real Monsters, Hey Arnold, The Angry Beavers, etc.) were all big during this era. As a result, the children born during this era, like myself, have a very serious and determined nature.
Neptune in Aquarius (1998-2012)
The technology culture. When Neptune in Aquarius hit, the internet and cell phones became mainstream, social media became a tool used by everyone (Myspace, Facebook, Twitter, and YouTube all have Neptune in Aquarius with Pluto in Sagittarius), and reality TV became a mainstay on TV, giving normal people the chance to become stars. Neptune in Aquarius was known for being the era of Nu Metal (like metal, but with DJs and turntables being used), indie rock, emo, and techno pop, while Boy Bands and bubblegum pop were also prevalent but more in tune with Pluto in Sagittarius. As a result, the children born during this era are very eccentric in nature.
Neptune in Pisces (2011-2026)
This transit is still ongoing, but some common themes of this era are a rise in alternative spirituality and the PC culture. Pisces rules compassion as well as sensitivity, so it's no coincidence that the PC culture only came into existence during the Neptune in Pisces era. With Pluto in Capricorn happening at the same time, exposing the corruption in government and big business and making knowledge of the Illuminati more mainstream, Neptune in Pisces is making alternative spirituality more mainstream, as an alternative to the organized religions controlled by the Illuminati (Islam, Judaism, Christianity, Catholicism, Mormonism, etc. are all man-made religions and are pitted against each other in order to divide and conquer... a (New World) Order out of chaos (division creates chaos).
Like with Pluto, all Neptune eras are connected. Extroverted Neptune in Leo came before depressing Neptune in Virgo, which came before peaceful Neptune in Libra, which came before cynical Neptune in Scorpio, which came before jovial Neptune in Sagittarius, which came before serious Neptune in Capricorn, which came before eccentric Neptune in Aquarius, etc., and when these Neptune generations become young adults, Pluto enters the sign their Neptune was in at birth, destroying the illusions they were conditioned with during their childhood (Neptune also rules illusions). Also notable is that the masculine Neptune eras are more upbeat than the feminine Neptune eras, which goes hand in hand with the masculine Neptune generations having a more outward image and expression than their feminine Neptune counterparts, which I've noticed in person. In 2026, Neptune will go into Aries for good, which will likely result in a more upbeat era once again.
Dates of Neptune in the signs: