| 100% | PLEISTOCENE | 11 | First epoch of the Quaternary period in geological time |
| 57% | OLIGOCENE | 9 | Third epoch of the Palaeogene period of geological time |
| 56% | MIOCENE | 7 | First geological epoch of the Neogene period |
| 56% | TRIASSIC | 8 | Geological time period of the first dinosaurs |
| 55% | HOLOCENE | 8 | In geology, the second epoch of the Quaternary period |
| 52% | MIOCENE | 7 | First epoch of the Neogene Period |
| 49% | PERMIAN | 7 | Last period of the Palaeozoic era in the geological time scale |
| 47% | EOCENE | 6 | Second epoch of the Palaeogene period in the geologic timescale |
| 44% | HOLOCENE | 8 | The current epoch of geological time |
| 43% | EXPOSURE | 8 | In photos, the period of time of light on film |
| 42% | ERA | 3 | Type of time period hidden in the word "generation" |
| 42% | ICEAGE | 6 | Part of the Quaternary Period |
| 41% | COEDS | 5 | Some University of Virginia undergrads in 1969, for the first time |
| 41% | CONTEMPORANEOUS | 15 | Occurring in the same period of time |
| 41% | EOCENE | 6 | Epoch of the Tertiary period |
| 41% | EOCENE | 6 | Epoch of the first horses |
| 41% | EOCENE | 6 | Epoch of the first whales |
| 41% | ELSA | 4 | One of two Disney characters singing "For the First Time in Forever" |
| 41% | PERMIAN | 7 | Last period of the Palaeozoic era in the geological timescale |
| 40% | ERA | 3 | Time period that's often the savior of many crossword constructors (as in this instance) |
| 40% | BART | 4 | First name of the only fictional character in Time's list of the 100 Most Important People of the Century |
| 39% | MIAS | 4 | Lucien —, captain of the France rugby union team that won the Five Nations outright for the first time in 1959 |
| 38% | PLIOCENE | 8 | Last epoch of the Tertiary period |
| 38% | JURASSIC | 8 | Period in the Age of Dinosaurs |
| 38% | YTD | 3 | Period of time from the first day of the year till today: Abbr. |
| 38% | HOLOCENE | 8 | Current epoch of geological time |
| 38% | EON | 3 | Period in the evolution of a planet |
| 38% | EPOCHS | 6 | Periods in time such as the Pleistocene |
| 38% | RON | 3 | First name of the anchorman in "Anchorman" |
| 38% | JIMINY | 6 | First name of the cricket in Pinocchio |