Calendar square
(Other definitions for date that I've seen before include "6 [TREE]" , "Estimate age of" , "Romantic assignation" , "Rendezvous" , "eg 1588" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">calendar square</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for day that I've seen before include "Twenty-four hours" , "24 hours" , "24 hour period" , "Born yesterday" , "Dawn to dusk" .)