This is a tentative Secular Selection Day.
The previous time reference for New Years was explicit about calling out the month as being your month. The only calendar that switches months at New Years is the modern Gregorian. The text then moves on and describes events for the 10th and 14th of that month. This is the first of the dates called out on the Gregorian Calendar.
Theoretical Time:
Associated Scripture:
2 Exodus 12:3-4
3Speak to all the congregation of Israel saying, On the 10th day of this month they will take to themselves every man a lamb for his own house, and a lamb for his father's house;
4and if the house is too little for the lamb, let him and his neighbor next to his house take it according to the number of the persons; every man according to the portion of his eating will make your count for the lamb.
Psalm 140 has an echo at this date and may be related.