Yule's Eve is the longest night of the year. I know most people put Midsummer's Eve as the night when fairies, sprites, pixies and other wee folk come out to play pranks and dance in the moonlight (and who am I to say they don't?); but I've always felt that fairy-land was somehow closest to ours during the Long Night. Something about the blue light of the moon, the ethereal frost and blowing mist, makes me think of the good folk.
Poul Anderson gives the best description of what I consider Yule's Eve in fairy-land as I've ever heard. From his short story, "Queen of Air and Darkness":
The last glow of the last sunset would linger until almost midwinter. But there would be no more day, and the northlands rejoiced. Blossoms opened, flamboyance on firethorn trees, steelflowers rising blue from the brok and rainplant that cloaked all hills, shy whiteness of kiss-me-never down in the dales. Flitteries darted among them on iridescent wings; a crownbuck shook his horns and bugled through warmth and flower odors. Between horizons the sky deepened from purple to sable. Both moons were aloft, nearly full, shining frosty on leaves and molten on waters. The shadows they made were blurred by an aurora, a great blowing curtain of light across half heaven. Behind it the earliest stars had come out.
I think I will welcome the Long Night with a glass (or two) of blackberry mead, and perhaps a nice cake...