元旦|がんたんgantan[0]heiban (flat)

1. nounNew Year's Day; first day of the year
   一いち年ねんの計けいは元旦がんたんにあり。↗

   New Year's Day is the key to the year.
2. nounNew Year's morning; morning of New Year's Dayorig. meaning

• Synonym元日がんじつNeutralCovers January 1 as a whole day and is the more formal term; 「元旦」 originally meant the morning of 「元日」.
• Related1月1日NeutralRefers simply to the calendar date January 1, stated objectively; 「元旦」 carries the festive feel of the year's first day.
• Antonym大晦日おおみそかNeutralMeans New Year's Eve, December 31 — the opposite end of the year from 「元旦」, the first day of the new year.

For January 1 in formal use say 「元日」; use 「元旦」 for the morning of the year's first day or in New Year greetings, as in 「元旦の朝」「年賀状の元旦」; New Year's Eve is 「大晦日」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 元日がんじつの朝あさ。一いち月がつ一日ついたちの朝あさ。
2. 元日がんじつ。