PSEC
| Date | Clue |
|---|---|
| 2021-04-16 | Tiny fraction of a min. |
| 2020-10-15 | Time it takes light to travel .3 mm: Abbr. |
| 2016-08-30 | Tiny fraction of a min. |
| 2013-09-29 | One 60-trillionth of a min. |
| 2011-12-07 | Tiny fraction of a min. |
| 2008-11-28 | Tiny fraction of a min. |
| 2004-10-13 | Infinitesimal division of a min. |
| 2001-06-24 | 1/60 of a trillionth of a min. |
| 1998-05-22 | Time it takes for light to travel .3 mm |