Crossword Genius

They mark time (9)

Ross

I believe the answer is:

calendars

I'm a little stuck... Click here to teach me more about this clue!

'they' is the definition.
Both the answer and definition are plural nouns.
Perhaps they are linked in a way I don't understand?

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for calendars that I've seen before include "Lists of days, weeks, months" , "Tabular arrays of days" .)

I've seen this clue in The Globe and Mail and The Irish News.
Want a hint initially instead of a full solution? Install my app