noun
Specifically the morning of New Year's Day. Often used in formal or literary contexts. Compare 元旦 (がんたん), which is more common.
See also: 元旦
歳旦の清々しい空気が好きだ。
I like the refreshing air of New Year's morning.
noun
Refers to the entire day of January 1st. Less common than 元旦 or 元日 in everyday speech.
歳旦には家族で集まる。
On New Year's Day, the family gets together.