A chronological timeline of the 20th Century as seen in the Primeverse. All listed events took place in both the original and post-original timeline unless otherwise stated.
- The 19th Century ended and the 20th Century started.
- The Victorian era ended.
- Patrick Quinn, under the guise of Ethan Dobrowski, appeared as an anarchist in Russia and murdered at least a half dozen people before disappearing, presumably through another Anomaly. 
- A flock of Terror Birds appeared near a Research Cabin via the local Cenozoic Anomaly and killed John Mortimer's three research colleagues before returning to their time. 
- World War II took place. 
- A research group (presumably the British Government) studied an Anomaly on Guns Island, and built an observatory post over it. 
- Jessica Parker was born. 
- Connor Temple stayed behind in a museum to see if the exhibits came to life at night, but only ended up locked in the toilet for three hours. 
- Patrick Quinn left the 20th Century, escaping a Camouflage Beast via the Brooks house Anomaly. The creature remained in the "present". 
- Nick Cutter and Helen Ambrose got married and both started working at the Central Metropolitan University. Nick specifically worked in the Department of Evolutionary Zoology. 
- Stephen Hart had an affair with Helen Cutter. 
- A Gorgonopsid appeared in the Forest of Dean via the local Permian Anomaly. The Gorgonopsid either remained in the "present" or returned to the Permian. Also, the Forest of Dean Anomaly either closed or remained open for the next 8 years.
- Helen Cutter left the 20th century, via the Forest of Dean Anomaly, to travel through the Anomalies. 
- The 20th century ended and the 21st Century started.
- The Cold War was said to have occurred. 
- The research group on Guns Island soon abandoned the island after the Anomaly closed some time after the Cold War ended, renouncing their claim to the island leaving France and Ireland to argue over ownership. 
- A Smilodon cub came through an Anomaly near Blue Sky Park in the 1990s or early 2000s. 
- Tom and Duncan
- The mercenary known as the Cleaner (presumably)
- Jack Maitland, Abby Maitland's brother, was born after 1985
- April Leonard
- ↑ Episode 4.6.
- ↑ Episode 3.6
- ↑ Mentioned in The Lost Island.
- ↑ Speculated in The Lost Island.
- ↑ Circa 1969 as James Lester was 41 in 2011.
- ↑ Circa 1969 as Danny Quinn was 41 in 2011.
- ↑ Circa 1971 as Joseph Wilder was 38 in 2009.
- ↑ Circa 1971 as Philip Burton was 40 in 2011.
- ↑ Circa 1972/1973 as Tom Ryan was 34 in 2006/2007.
- ↑ Circa 1973, as Nick Cutter was confirmed to be 36 in 2009 by the producers.
- ↑ Circa 1973, as Helen Cutter was confirmed to be 36 in 2009 by the producers. However, Helen spent an unconfirmed amount of time traveling through the Anomalies so her age would almost certainly be distorted from the number of years in the 'present' since she was born.
- ↑ Circa 1974 as Oliver Leek was 33 in 2007.
- ↑ Circa 1974 as Christine Johnson was 35 in 2009.
- ↑ Born between March 1974 and March 1975, as Stephen Hart was 32 in March 2007, as seen on his grave. (Episode 2.7)
- ↑ Circa 1979/1980 as Claudia Brown was 27 in 2006/2007.
- ↑ Circa 1979/1980 as Jenny Lewis was presumably the same age as Claudia Brown.
- ↑ Circa 1981 as Sarah Page was 29 in 2010
- ↑ Circa 1981 as Patrick was confirmed to be 14 in 1995. Patrick spent around 18 years traveling through the Anomalies so his age was distorted by 2 years he arrived in 2011.
- ↑ Circa 1983 as Connor Temple was 28 in 2011.
- ↑ Circa 1985 as Abby Maitland was 26 in 2011.
- ↑ Circa 1985, as Caroline Steel was 22 in 2007.
- ↑ Circa 1985, as Hilary Becker was 26 in 2011.
- ↑ Circa 1991 as Jess Parker was 21 in 2011.
- ↑ Episode 3.1
- ↑ Episode 3.2
- ↑ Series 1
- ↑ Episode 1.6
- ↑ Episode 1.1
- ↑ Series 1
- ↑ The Lost Island
- ↑ The Lost Island
- ↑ Episode 2.3