first dream of the New Year
Refers to the dream one has on the night of January 1st or 2nd, traditionally believed to foretell the year's fortune. Often associated with the saying 一富士二鷹三茄子 (first Mt. Fuji, second a hawk, third an eggplant) as auspicious dream subjects.
Mt. Fuji appeared in my first dream of the New Year.
They say that if you see something auspicious in your first dream of the year, the whole year will be a good one.
dream on the night of Setsubun
Archaic usage; historically referred to the dream on the night of Setsubun (the day before the beginning of spring), which was also considered significant for fortune-telling. Now largely replaced by the New Year's dream meaning.
See also: 節分
In old documents, the dream seen on the night of Setsubun was also called 'hatsuyume'.
I had a very good first dream this New Year.
It's said to be auspicious if Mt. Fuji appears in your first dream of the year.