day

https://doi.org/10.1351/goldbook.D01527
Non-SI unit of time, \(\rm{d}=86\ 400\ \rm{s}\). The day is not exactly defined in terms of the second since so-called leap seconds are added or subtracted from the day semiannually in order to keep the annual average occurrence of midnight at 24:00 on the clock.
Sources:
Green Book, 2nd ed., p. 111 [Terms] [Book]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 968 [Terms] [Paper]
Citation: 'day' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.D01527 RIS BibTex EndNote
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