Crossword Genius

In which one's days are numbered? (8)

Ross

I believe the answer is:

calendar

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

'one's days are numbered?' is the definition.
(as in dates given in a calendar)

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

Can you help me to learn more?

(Other definitions for calendar that I've seen before include "List of days etc" , "list of appointments" , "Chart of times" , "Table of the days of a year" , "List of dates of land race" .)

I've seen this clue in The Sun.
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