A day subsequent in time to a given event by some significant period other than a year (especially as prefixed by the amount of time in question).
A day that is an exact number of years (to the day) since a given significant event occurred. Often preceded by an ordinal number indicating the number of years.
Such a day that commemorates a wedding.
One day of sidereal time; the time in which Earth rotates once around its axis, relative to the point of the vernal equinox (about 23 hours, 56 minutes, 4 seconds).
The rotational period of Earth; the time in which Earth rotates around its axis 360 degrees.