Mary Lincoln Extra Credit Questions

[Anita]

No Googling please.

Mary Lincoln wrote:
My Dear Friend,
"For some time past, I have intended writing you, but each day has brought its own
separate calls, causing a delay, which has been unintentional. I have only a few moments, now at my disposal, it is quite late in the evening & tomorrow I must rise early, as it is_______.

Excerpt from second paragraph.
"...Speaking of boys, Willie's [ninth] birthday came off on the 21st of
Dec. and as I had long promised him a celebration, it duly came off. Some 50 or 60 boys & girls attended the gala, you may believe I have come to the conclusion, that they are nonsensical affairs. However, I wish your boys, had been in their midst..."

What was the reason Mary "had to rise early tomorrow."
Hint: It's not a date but a specific day.
Bonus: To whom was the letter addressed?