+"28d" commonly refers to a period of twenty-eight [Days](/wiki/Day). This duration is a recurring measure, notably marking the average length of a [Menstrual cycle](/wiki/Menstrual_cycle) in humans. It also appears in various natural phenomena and standardized schedules.
+## See also
+- [Cycle](/wiki/Cycle)
+- [Time](/wiki/Time)
+- [Calendar](/wiki/Calendar)
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