Assertion: calendar's day | /r/HasProperty | added
Facets:
Source sentences:
text: It required a group of people to decide when days should be added or removed in order to keep the calendar in sync with the astronomical seasons, marked by equinoxes and solstices.
text: The extra day was added, he says, because 1800 had 366 days in the Julian calendar but only 365 in the Gregorian calendar.