Lunar calendar traces of its origin in the earlier lunar calendar, which continued to be used alongside it for religious and agricultural purposes. Present-day lunisolar calendars include the Chinese, Hindu, and Thai calendars. Synodic months are 29 or 30 days in length, making a lunar year of 12 months about 11 days shorter than a solar year. Some lunar calendars do not use intercalation, such as most Islamic calendars. For those that do, such as the Hebrew calendar, the most common form of intercalation is to add an additional month every second or third year. Some lunisolar calendars are also calibrated by
Thomas Fuller (mental calculator) skill was even used as proof that enslaved Blacks were equal to whites in intelligence, which fueled some pro-abolitionist discussion. When Fuller was about 70 years old, William Hartshorne and Samuel Coates of Pennsylvania were in Alexandria and, having heard of Fuller's powers, sent for him. They asked him two questions which satisfied their curiosity. First, when they asked him how many seconds there were in a year and a half, he answered in about two minutes, 47,304,000. Second, when they asked how many seconds a man has lived who is 70 years, 17 days and 12 hours old, he