During the flashback when Darla turns Angel into a vampire, the date is said to be 1753. However, in season one we find out that in 1775 Angel was in his 20s and still human.
The episode begins with Buffy having short bangs. When she goes to invite Faith to Christmas Eve dinner, her hair style is longer/different. Buffy goes back to having short bangs after visiting Faith.
When it starts to snow, it shows Xander sleeping outside on the fresh grass with flurries. The scene changes to Buffy and Angel walking down the thickly snow covered road.
Buffy and Angel are outside when the snowfall starts, you can hear someone walk next to them when there is supposed to be nobody there.
The First is often seen touching or caressing Angel, however it is later revealed in season 7 that the First is non-corporeal and, therefore, would not have been able to touch anything.