Timeline
A Geological & Historical Time Scale timeline. Filter by section or type, and optionally show only periods that have History Prime articles.
Tip: toggle Articles only to show only periods that contain History Prime articles.
Geological Time
Human History
Other Periods (Informal)
Frontier Technologies (Themes)
Calendar Systems
Timeline FAQ
What is an Eon?
An Eon is the largest standard division of geologic time. Eons contain multiple
eras and can span hundreds of millions to billions of years.
What is an Era?
An Era is a major subdivision of an eon, used to group long stretches of Earth
history
with broad, recognizable changes in geology and life. Eras are divided into
periods.
What is a Period?
A Period is a subdivision of an era. Periods are commonly used in geology and
paleontology
(for example, the Jurassic is a Period) and are divided into epochs.
What is an Epoch?
An Epoch is a subdivision of a period. Epoch boundaries often reflect clear
shifts in the
rock record and fossil evidence, and epochs are divided into ages.
What is an Age?
In geology, an Age is a subdivision of an epoch (often paired with the term
Stage in rock layers). It’s one of the smallest commonly used
formal
time units.
On this timeline, Age can also be used in a historical sense (e.g., “Bronze Age”), which is a human-history label rather than an official geologic unit.
On this timeline, Age can also be used in a historical sense (e.g., “Bronze Age”), which is a human-history label rather than an official geologic unit.
What does Informal mean?
Informal labels are useful, popular, or emerging terms that aren’t
officially
defined as
part of the formal geologic time scale (or don’t have broad scholarly consensus). They can
still
be valuable
for discussion and navigation.
Example: “Anthropocene” is widely used, but it was not approved as a formal geological epoch by the IUGS/ICS process.
Example: “Anthropocene” is widely used, but it was not approved as a formal geological epoch by the IUGS/ICS process.
What is a Theme?
A Theme is a cross-cutting category used to group related stories across
different times and
regions (e.g., Artificial Intelligence, Cybersecurity,
Biotechnology). Themes are
navigation hubs — they don’t represent a single continuous time unit.
What is a Calendar System?
A Calendar system is a structured way to organize time into days, months, and years
for
scheduling, record-keeping, and festivals.
Some calendars are solar (aligned to Earth’s orbit and seasons), some are lunar (aligned to Moon phases), and some are lunisolar (Moon months adjusted to stay seasonal with leap months). Many cultures also use era/year-numbering systems (like regnal years or Buddhist Era) on top of a civil calendar.
Some calendars are solar (aligned to Earth’s orbit and seasons), some are lunar (aligned to Moon phases), and some are lunisolar (Moon months adjusted to stay seasonal with leap months). Many cultures also use era/year-numbering systems (like regnal years or Buddhist Era) on top of a civil calendar.