Refers specifically to the morning of New Year's Day. Cross-referenced with 元朝 (がんちょう), a more formal term for the same concept.
See also: 元朝 (がんちょう)
On New Year's morning, the whole family eats osechi cuisine together.
Compound of 年 (とし, 'year') + の (possessive particle) + 朝 (あした, 'morning'). The reading あした for 朝 is an older form; modern Japanese usually uses あさ.