1Exposure to sunlight, or a place that receives good sunlight; used to describe how sunny a room, garden, etc. is.
このマンションは日当たりが良くて、冬でも暖かい。
This apartment gets good sunlight, so it's warm even in winter.
日当たりの良い場所に鉢植えを置いた。
I put the potted plant in a sunny spot.
北向きの部屋は日当たりが悪い傾向がある。
North-facing rooms tend to get poor sunlight.
2Per day — an older way of expressing an amount or rate for one day (e.g. "5,000 yen per day").
アルバイトの日当たりは五千円だった。
The daily pay for the part-time job was 5,000 yen.