Geologic Time Converter
Type an age in Ga, Ma, ka or years to convert every unit and see its eon, era, period and epoch on the ICS v2024/12 chart, with boundary ages and chart colours. The same age is also placed on Earth history squeezed into one calendar year, a 24-hour day and a timeline of your chosen length.
In geology, Ma (mega-annum) is one million years, Ga (giga-annum) is one billion years and ka (kilo-annum) is one thousand years, so 66 Ma means 66 million years ago.
Use the Geologic Time Converter
Unit Converter
Elapsed-duration conversion. A non-negative value can also be interpreted as an age before present.
Earth age interpretation
66 Ma- Eon
- Phanerozoic
- Era
- Cenozoic
- Period / epoch
- Paleogene – Paleocene
- Spans
- 66–56 Ma
- Context
- Mammals diversify after the K–Pg extinction
Deep time, squeezed
Earth history (4,567 Myr) as one year, one day and a timeline.
- 1-year calendar
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- Before New Year
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- 24-hour clock
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- From the present end
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Ages in Ma (million years ago) from the ICS International Chronostratigraphic Chart v2024/12, to epoch (series) level in the Phanerozoic; ~ marks approximate ages. Colours follow the CGMW. Select a row to load its start age.
| Eon | Era | Period | Epoch | Start (Ma) | Duration |
|---|---|---|---|---|---|
| Phanerozoic | Cenozoic | Quaternary | Holocene | 0.0117 | 11.7 kyr |
| Phanerozoic | Cenozoic | Quaternary | Pleistocene | 2.58 | 2.57 Myr |
| Phanerozoic | Cenozoic | Neogene | Pliocene | 5.333 | 2.75 Myr |
| Phanerozoic | Cenozoic | Neogene | Miocene | 23.04 | 17.71 Myr |
| Phanerozoic | Cenozoic | Paleogene | Oligocene | 33.9 | 10.86 Myr |
| Phanerozoic | Cenozoic | Paleogene | Eocene | 56 | 22.1 Myr |
| Phanerozoic | Cenozoic | Paleogene | Paleocene | 66 | 10 Myr |
| Phanerozoic | Mesozoic | Cretaceous | Upper | 100.5 | 34.5 Myr |
| Phanerozoic | Mesozoic | Cretaceous | Lower | 143.1 | 42.6 Myr |
| Phanerozoic | Mesozoic | Jurassic | Upper | 161.5 | 18.4 Myr |
| Phanerozoic | Mesozoic | Jurassic | Middle | 174.7 | 13.2 Myr |
| Phanerozoic | Mesozoic | Jurassic | Lower | 201.4 | 26.7 Myr |
| Phanerozoic | Mesozoic | Triassic | Upper | ~237 | ~35.6 Myr |
| Phanerozoic | Mesozoic | Triassic | Middle | 246.7 | ~9.7 Myr |
| Phanerozoic | Mesozoic | Triassic | Lower | 251.902 | 5.2 Myr |
| Phanerozoic | Paleozoic | Permian | Lopingian | 259.51 | 7.61 Myr |
| Phanerozoic | Paleozoic | Permian | Guadalupian | 274.4 | 14.89 Myr |
| Phanerozoic | Paleozoic | Permian | Cisuralian | 298.9 | 24.5 Myr |
| Phanerozoic | Paleozoic | Carboniferous | Pennsylvanian | 323.4 | 24.5 Myr |
| Phanerozoic | Paleozoic | Carboniferous | Mississippian | 358.86 | 35.46 Myr |
| Phanerozoic | Paleozoic | Devonian | Upper | 382.31 | 23.45 Myr |
| Phanerozoic | Paleozoic | Devonian | Middle | 393.47 | 11.16 Myr |
| Phanerozoic | Paleozoic | Devonian | Lower | 419.62 | 26.15 Myr |
| Phanerozoic | Paleozoic | Silurian | Pridoli | 422.7 | 3.08 Myr |
| Phanerozoic | Paleozoic | Silurian | Ludlow | 426.7 | 4 Myr |
| Phanerozoic | Paleozoic | Silurian | Wenlock | 432.9 | 6.2 Myr |
| Phanerozoic | Paleozoic | Silurian | Llandovery | 443.1 | 10.2 Myr |
| Phanerozoic | Paleozoic | Ordovician | Upper | 458.2 | 15.1 Myr |
| Phanerozoic | Paleozoic | Ordovician | Middle | 471.3 | 13.1 Myr |
| Phanerozoic | Paleozoic | Ordovician | Lower | 486.85 | 15.55 Myr |
| Phanerozoic | Paleozoic | Cambrian | Furongian | ~497 | ~10.15 Myr |
| Phanerozoic | Paleozoic | Cambrian | Miaolingian | ~506.5 | ~9.5 Myr |
| Phanerozoic | Paleozoic | Cambrian | Series 2 | ~521 | ~14.5 Myr |
| Phanerozoic | Paleozoic | Cambrian | Terreneuvian | 538.8 | ~17.8 Myr |
| Proterozoic | Neoproterozoic | Ediacaran | — | ~635 | ~96.2 Myr |
| Proterozoic | Neoproterozoic | Cryogenian | — | ~720 | ~85 Myr |
| Proterozoic | Neoproterozoic | Tonian | — | 1,000 | ~280 Myr |
| Proterozoic | Mesoproterozoic | Stenian | — | 1,200 | 200 Myr |
| Proterozoic | Mesoproterozoic | Ectasian | — | 1,400 | 200 Myr |
| Proterozoic | Mesoproterozoic | Calymmian | — | 1,600 | 200 Myr |
| Proterozoic | Paleoproterozoic | Statherian | — | 1,800 | 200 Myr |
| Proterozoic | Paleoproterozoic | Orosirian | — | 2,050 | 250 Myr |
| Proterozoic | Paleoproterozoic | Rhyacian | — | 2,300 | 250 Myr |
| Proterozoic | Paleoproterozoic | Siderian | — | 2,500 | 200 Myr |
| Archean | Neoarchean | — | — | 2,800 | 300 Myr |
| Archean | Mesoarchean | — | — | 3,200 | 400 Myr |
| Archean | Paleoarchean | — | — | 3,600 | 400 Myr |
| Archean | Eoarchean | — | — | 4,031 | 431 Myr |
| Hadean | — | — | — | 4,567 | 536 Myr |
| Symbol | Full Name | Equals (years) |
|---|---|---|
| Ga | Gigaannum | 1,000,000,000 |
| Ma | Megaannum | 1,000,000 |
| ka | Kiloannum | 1,000 |
| yr | Year | 1 |
| dec | Decade | 10 |
| cent | Century | 100 |
| mil | Millennium | 1,000 |
Notation note
Age and duration are different. This converter uses the same decimal factors for arithmetic, but only non-negative ages from 0 to 4,567 Ma are mapped to Earth-history intervals. The term “yr BP” is especially associated with radiocarbon reporting; do not assume every elapsed duration has a 1950 CE epoch.
Quick answer
In geology, Ma (mega-annum) is one million years, Ga (giga-annum) is one billion years and ka (kilo-annum) is one thousand years, so 66 Ma means 66 million years ago. On the ICS chart v2024/12 the Phanerozoic starts at 538.8 Ma, the Mesozoic at 251.902 Ma, the Cenozoic at 66.0 Ma and the Holocene 11,700 years ago. If Earth history were one year, the dinosaurs would die out on Dec 26.
Examples
| Age | Years | Marks | On a 1-year calendar |
|---|---|---|---|
| 4.567 Ga | 4,567,000,000 | Hadean begins | Jan 1, 00:00 |
| 538.8 Ma | 538,800,000 | Cambrian begins | Nov 18 |
| 251.902 Ma | 251,902,000 | Triassic begins | Dec 11 |
| 66 Ma | 66,000,000 | Paleogene begins | Dec 26, 17:24 |
| 11.7 ka | 11,700 | Holocene begins | 81 s before midnight |
Type a value in Ga, Ma, ka or years to convert it and see its eon, era, period, epoch and calendar position.
Summary
Geologists write ages with SI-style prefixes on the annum: ka for thousand, Ma for million and Ga for billion years. This converter turns any value into every unit and, for ages from the present back to 4,567 Ma, looks it up on the International Commission on Stratigraphy's International Chronostratigraphic Chart v2024/12: eon, era, period and, in the Phanerozoic, the epoch or series, with boundary ages and the official CGMW colours. Ages marked ~ are approximate because the boundary has no ratified numerical age. To make deep time easier to picture, the same age is mapped onto Earth history compressed into one calendar year, a 24-hour day, and a timeline of any length you choose. Numerical boundary ages are revised as dating improves; the chart version is stated so you can cite it.
How it works
- Type a number into any unit field (Ga, Ma, ka, years, millennia, centuries or decades); the others update instantly.
- For an age between 0 and 4,567 Ma, the interpretation card shows its eon, era, period and epoch with boundary ages and chart colour.
- The deep-time card places the age on a one-year calendar, a 24-hour clock and a timeline of the length you enter.
- Browse the full time scale table, from the Holocene to the Hadean, with start ages and durations.
- Select any row to load its start age into the converter.
Use cases
- Convert Ma, Ga and ka values from papers into years.
- Find which period and epoch a fossil or rock age falls in.
- Get boundary ages for geologic periods from the current ICS chart.
- Explain deep time with the Earth-history-in-a-year calendar or a classroom timeline.
- Plan a scaled geologic time rope or hallway timeline.
- Check the start and length of the Cambrian, Jurassic, Cretaceous or other periods.