| Periods worth remembering | 25 |
| Periods when the computers work | 31 |
| Periods when strikes are called | 31 |
| Periods when many go to lunch | 29 |
| Periods when Harry Potter books are unavailable? | 48 |
| Periods used with ordinal nos. | 30 |
| Periods upon periods | 20 |
| Periods spent using a batting-practice bat? | 43 |
| Periods preceding big events | 28 |
| Periods prec. soccer shootouts | 30 |
| Periods on jobs | 15 |
| Periods of warming ... or cooling off | 37 |
| Periods of unrest | 17 |
| Periods of turmoil | 18 |
| Periods of time: Abbr. | 22 |
| Periods of time | 15 |
| Periods of the academic year | 28 |
| Periods of sunlight | 19 |
| Periods of sullenness | 21 |
| Periods of sudden death: Abbr. | 30 |
| Periods of service | 18 |
| Periods of seedings and plantings | 33 |
| Periods of rising prices for securities | 39 |
| Periods of revolution? | 22 |
| Periods of relief | 17 |
| Periods of rain, often | 22 |
| Periods of prosperity | 21 |
| Periods of prayer? | 18 |
| Periods of powerlessness | 24 |
| Periods of power | 16 |
| Periods of pious seclusion | 26 |
| Periods of penitence | 20 |
| Periods of note | 15 |
| Periods of milit. service | 25 |
| Periods of mania | 16 |
| Periods of light | 16 |
| Periods of interest | 19 |
| Periods of intense pressure | 27 |
| Periods of inactivity | 21 |
| Periods of importance | 21 |
| Periods of immaturity | 21 |
| Periods of history on a timeline | 32 |
| Periods of history | 18 |
| Periods of historical note | 26 |
| Periods of highest vigor | 24 |
| Periods of grief | 16 |
| Periods of great success | 24 |
| Periods of good fortune | 23 |
| Periods of fasting | 18 |
| Periods of extra mins. | 22 |
| Periods of duty at sea | 22 |
| Periods of distinction | 22 |
| Periods of development | 22 |
| Periods of decline | 18 |
| Periods of de-escalation, perhaps | 33 |
| Periods of calm | 15 |
| Periods of boredom | 18 |
| Periods of abstinence | 21 |
| Periods just past sunset | 24 |
| Periods just past midnight | 26 |
| Periods in stark contrast to global warming | 43 |
| Periods in prison, e.g. | 23 |
| Periods in office | 17 |
| Periods in history | 18 |
| Periods in contrast to global warming | 37 |
| Periods immediately before | 26 |
| Periods from Dec. 24 to Jan. 6 | 30 |
| Periods for geologists | 22 |
| Periods for Aries and Taurus | 28 |
| Periods divide them | 19 |
| Periods beyond record | 21 |
| Periods between Winter and Summer Olympics | 42 |
| Periods between wars | 20 |
| Periods between vernal equinoxes | 32 |
| Periods added to harmonize the lunar and solar calendars | 56 |
| Periods | 7 |
| Periodontists' org. | 23 |
| Periodontists' grp. | 23 |
| Periodontist's recommendation | 33 |
| Periodontist's org. | 23 |
| Periodontist's grp. | 23 |
| Periodontist's focus | 24 |
| Periodontist's deg. | 23 |
| Periodontist's concerns | 27 |
| Periodontist's concern | 26 |
| Periodontal concerns | 20 |
| Periodontal concern | 19 |
| Periodonist's concern | 25 |
| Periodicals, for short | 22 |
| Periodicals, briefly | 20 |
| Periodicals with unturnable pages | 33 |
| Periodicals on a PC | 19 |
| Periodicals not brought by a postal carrier | 43 |
| Periodicals | 11 |
| Periodically war-torn Turkish city | 34 |
| Periodically rising and falling | 31 |
| Periodically flowing and ebbing | 31 |
| Periodically available fast food item | 37 |
| Periodically | 12 |
| Periodical: Abbr. | 17 |