| Age |
| Era |
| Cycle |
| Period |
| Timespan |
| Time ___ |
| Long time |
| Big period |
| Time-period |
| Period part |
| Period piece |
| Era's advent |
| Eocene, e.g. |
| Ages and ages |
| Historic time |
| Geologic span |
| Geologic time |
| Important age |
| Momentous era |
| Memorable era |
| Historical era |
| Notable period |
| Memorable time |
| Period of note |
| Dawn of an age |
| Pliocene, e.g. |
| Dawn of an era |
| Period of time. |
| Years and years |
| Long, long time |
| Geologic period |
| Historic period |
| Geological span |
| Geological time |
| Particular time |
| Noteworthy time |
| Historical time |
| Span in history |
| Eocene, for one |
| Division of time |
| Many, many years |
| Time to remember |
| Important period |
| Extended period? |
| Golden age, e.g. |
| Momentous period |
| Prominent period |
| Distinctive time |
| Timeline segment |
| Significant time |
| Memorable period |
| A memorable date |
| Part of a period |
| Miocene, for one |
| Period of history |
| Geological period |
| Historical period |
| Period in history |
| Notable time span |
| Memorable stretch |
| Noteworthy period |
| Pliocene, for one |
| Date of reference |
| Eocene or Neocene |
| Geologist's study |
| Holocene, for one |
| Pleistocene, e.g. |
| Distinctive period |
| Geologic time unit |
| Historical segment |
| Historical stretch |
| Significant period |
| Eocene or Pliocene |
| Pleistocene is one |
| Historic beginning |
| Pleistocene period |
| Long period of time |
| Geological division |
| Paleontology period |
| Notable time period |
| Late Jurassic, e.g. |
| Miocene or Pliocene |
| Period in cosmology |
| Pliocene or Miocene |
| The Eocene, for one |
| Geological time unit |
| Geologist's division |
| Geologic time period |
| Pleistocene, for one |
| Unit of geologic time |
| Earth science chapter |
| Geologist's time span |
| Signal period of time |
| Geological time period |
| Notable historic period |
| Geologicial time period |
| Several ages, in geology |
| Unit of geological time |
| Period of time in history |
| A unit of geological time |
| Long geologic time period |
| Distinctive period of time |
| Unit of geological time |
| Important historical period |
| A notable period of history |
| Noteworthy period of history |
| Moment in time, in astronomy |
| Distinctive period of history |
| Division of a geologic period |
| Distinctive historical period |
| Part of a period, geologically |
| Period on a geologic time scale |
| Beginning of era or long time period |
| Chapter in a geology textbook, perhaps |
| Point in time fixed by some great event |