OK, I know it means different things to different folks. I like the shortest day of the year because it means that the brightest days are ahead! I hope the coming bright days bring nice things to all of you.
Whoops, almost forgot we were bi-hemispherical here…May the increased starlight bring happiness to you who are south of the equator. 
I too especially enjoy celebrating the solstices and equinoxes … and Midsummer Night!
Sol Invicta (“The Sun is Unconquerable”) is the pagan holiday that’s linked to astronomical observation that the days, in fact, are getting longer again.
At one point, it seems, not everyone was so certain that the seasonal cycle would repeat. Can you imagine ~truly~ being worried that the days would just get shorter and shorter until Endless Night arrived?
shiver
The first observation of a lengthening day might be on either the 22nd or 23rd of December. But human error and astronomical measurements being what they were, I understand that it was considered politically astute to wait until a second confirming measurement was taken on the 23rd or 24th.
And then it was considered politically expedient to do the calculation on the night of the 24th, make the announcement, and celebrate on December 25th … the alternative was to have to explain why the seers knew in some years on the 24th and in others on the 25th.
What I know is that I wish that right now I was semi-naked in the sand under the hot sun. It’s cold and windy and damp here in Chicago, and if I didn’t live here I’d be someplace else!
Happy RamaHanuKwanziMas!
Cheers
MarkL