| Mayan and Mundane | 17 |
| Important chapters in history | 29 |
| History units | 13 |
| Historical chapters | 19 |
| Historic time periods | 21 |
| Geologists' studies | 23 |
| Geologists' periods | 23 |
| Geological time spans | 21 |
| Geological time series | 22 |
| Extended periods | 16 |
| Eventful times in history | 25 |
| Eon divisions | 13 |
| Distinctive historical periods | 30 |
| Chronology sections | 19 |
| Cenozoic and Mesozoic | 21 |
| Blocks of history | 17 |
| Baroque and classical | 21 |
| "-zoic" things | 24 |
| Victorian and Romantic, for two | 31 |
| Victorian and Mesozoic | 22 |
| Victorian and Elizabethan, e.g. | 31 |
| Victorian and Edwardian, for two | 32 |
| Victorian and Edwardian | 23 |
| Victorian and Cenozoic | 22 |
| Varro and Vulgar | 16 |
| Two-term presidents' terms, e.g. | 36 |
| Times to live through | 21 |
| Times on a timeline | 19 |
| Times gone by | 13 |
| Time-line segments | 18 |
| They're full of dates | 25 |
| They're a part of history | 29 |
| Swing and others | 16 |
| Swing and Christian | 19 |
| Specific times in history | 25 |
| Some are named for presidents | 29 |
| Some are named for music genres | 31 |
| Significant time spans | 22 |
| Significant time periods | 24 |
| Significant spans | 17 |
| Remembered periods | 18 |
| Reconstruction and horse-and-buggy | 34 |
| Presidencies, to historians | 27 |
| Precambrian et al. | 18 |
| Points in time | 14 |
| Pitching stats, for short | 25 |
| Pitchers' concerns | 22 |
| Pitchers want low ones | 22 |
| Pitchers try to keep them low | 29 |
| Pitcher's figs. | 19 |
| Pieces of history | 17 |
| Pickoffs lower them | 19 |
| Periods of interest | 19 |
| Periods of historical note | 26 |
| Period pieces? | 14 |
| Parts of history | 16 |
| Parts of eons | 13 |
| Particular periods | 18 |
| Paleozoic and Mesozoic, e.g. | 28 |
| Paleozoic and Cenozoic | 22 |
| Noteworthy stretches | 20 |
| Notable times in history | 24 |
| Notable historical spans | 24 |
| Mesozoic et al. | 15 |
| Mesozoic and Victorian | 22 |
| Mesozoic and Cenozoic, for two | 30 |
| Memorable stretches | 19 |
| Major spans | 11 |
| Major divisions of geological time | 34 |
| K's lower them | 18 |
| Important times in history | 26 |
| Important time periods | 22 |
| Important ages | 14 |
| Horse-and-buggy and others | 26 |
| History divisions | 17 |
| History 101 subjects | 20 |
| Historical study | 16 |
| Historic stretches of time | 26 |
| Historic segments | 17 |
| Historian's divisions | 25 |
| Guidry stats. | 13 |
| Greek and Roman | 15 |
| Geologists' divisions | 25 |
| Geologic slices of time | 23 |
| Gay Nineties and Roaring Twenties | 33 |
| Gay '90s and the like | 25 |
| Five geological periods | 23 |
| Eventful timeline divisions | 27 |
| Eventful periods | 16 |
| Epochal segments | 16 |
| Eoarchean and Neoarchean are two | 32 |
| Elizabethan and Big Band | 24 |
| Distinctive periods of history | 30 |
| Distinct times | 14 |
| Distinct time spans | 19 |
| Diocletian and Julian | 21 |
| Christian and others | 20 |
| Christian and Caesarean | 23 |
| Chapters in a history book, perhaps | 35 |
| Cenozoic and Mesozoic, e.g. | 27 |