KanjiJLPT N1
Daybreak

daybreak, dawn, morning

Mnemonic

The sun sits right on top of one horizontal line — the earth's edge. The instant sun lifts off that one razor-thin boundary, Daybreak erupts, flooding everything in warm amber light.
Additional thoughts
Picture the kanji literally: the sun (日) resting on one flat stroke (一) like a horizon line. Sun + horizon = daybreak. The shape tells the whole story.
Quick recall
Sun perched on one horizon line signals daybreak.

Details

The keyword for 旦 is daybreak. This kanji depicts the sun rising above the horizon, capturing the moment when the first light of day appears. It represents the early morning, specifically the time of dawn when the sun has just emerged. In broader usage, it can also refer to the morning or the beginning of a new day.
On'yomi
たん、だん
Kun'yomi
あき.らか、あきら、ただし、あさ、あした