nychthemeron

n. day, 24 hours, period of time of one day and one night (from Greek)

Nychthemeron or nycthemeron or nuchthemeron (from Greek nykt- "night", (h)emera "day") is a period of 24 consecutive hours. It is sometimes used, especially in technical literature, to avoid the ambiguity inherent in the term "day."It is the period of time that a calendar normally labels with a date.
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A period of 24-hours