Tabular arrays of days (9)
I believe the answer is:
calendars
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tabular arrays of days</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for calendars that I've seen before include "Tabular arrays of days" , "Lists of days, weeks, months" .)