Are such days at the end of three months? (5)

I believe the answer is:

ember

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'end of three months?' is the definition.
(September, November and December)

I can't explain the remainder of the clue.

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(Other definitions for ember that I've seen before include "what causes a warm glow" , "Smouldering piece left over from a fire" , "Small piece of glowing coal in a dying fire" , "something that glows" , "Glowing cinder" .)

I've seen this clue in the Evening Standard.

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