Leap Year
The image shows screen shots from stellarium web site on December 19 @ 23:56 for each of the years indicated.
Note the red arrow pointing to the space between the Sun and what may be a nebula (blue circle). 1 day drift over 4 years?
Noteable events on December 19:
1675 – The Great Swamp Fight, a pivotal battle in King Philip's War, gives the English settlers a bitterly won victory.
1776 – Thomas Paine publishes one of a series of pamphlets in The Pennsylvania Journal entitled "The American Crisis".
1941 – World War II: Adolf Hitler appoints himself as head of the Oberkommando des Heeres.
1998 – President Bill Clinton is impeached by the United States House of Representatives, becoming the second President of the United States to be impeached.