morning, noon, and night; all day long
Refers to the three main parts of the day as a set, often implying 'throughout the day' or 'from morning till night'.
I work nonstop morning, noon, and night.
Please take this medicine morning, noon, and night.
breakfast, lunch, and dinner; three meals a day
Abbreviation for 朝ご飯・昼ご飯・晩ご飯. Used informally to refer to the three daily meals as a set.
Are you eating breakfast, lunch, and dinner properly?
Eating out for all three meals gets expensive.
Compound of 朝 (あさ, morning), 昼 (ひる, noon), and 晩 (ばん, evening). The reading ひる becomes voiced to びる due to rendaku. The second sense is an abbreviation of 朝ご飯・昼ご飯・晩ご飯.