Today is the holy day of Yud Tes Kislev, the day that the first Chabad Rebbe, the Alter Rebbe, was released from prison in czarist Russia. Hence the name chag hageulah: the holiday of liberation.
It is also considered the Rosh Hashanah of Chassidus because once the Alter Rebbe was released from prison he was able to spread the teachings of Chassidus. And we know from the Baal Shem Tov that when the wellsprings of Chassidus are spread to the entire world Moshiach will come.
So today is a day connected with Moshiach and redemption and tremendous light.