The Cretaceous Ended in Springtime! 

THIS ARTICLE gives convincing evidence that the Cretaceous ended on a spring day. I am not sure whether it was morning or evening.

It is based on THIS PAPER in which the authors, studying fish fossils, speculate that bone growth had just restarted after a winter pause. The fish had died while ingesting spherules caused by the asteroid impact at Chicxulub - within hours of the impact. 

To get a more easily digested summary of their findings I recommend THIS PODCAST by one of the papers authors, Jan Smit. The illustrations supporting the podcast are superb.

Another podcast on this comes from Nature. You can find it HERE. The lead author of the original paper, Melanie During, talks about the selectivity of the extinction - creatures on the surface died, those in burrows escaped. So maybe it happened at night!?

Maps of the Tanis site in North Dakota.  A: Regional context showing the large sea covering central North America during the Cretaceous.  The map shows previously known tsunami locations (black dots) and the Tanis site (star) on an ancient river draining into the inland sea.  B: Photo and interpretation showing the 2.5-meter-thick surge event deposit overlying sandstone deposited as a point-bar in the Tanis river.  C: Diagram (not to scale) of the event deposit setting.  The event deposit (1) covers the slope of a sandy bar of a meander (2).  The densest carcass accumulations (3) were found just below Cretaceous-Paleogene boundary deposits (4) that directly overlay the event deposit.

DePalma et al., PNAS, (2019) 116, 8190