Today is the longest day of the year where everyone in the northern hemisphere will appreciate more hours and minutes of sunlight today. The word Solstice, comes from the Latin: Sol=Sun, and Stice, from the verb sistere=to stand still. So the Sun will stand still for 72 hours.
Our Ancestors, and some people today use the solstices as markers of time and the functioning of certain Celestial events; for instance in Kemet (Egypt), the Summer Soltice was the most important day of the year. When the Sun was at its zenith (highest point in the sky), the people of Kemet new that it was the beginning of the rising of the Nile River; the rising of the Nile signaled the coming floods which would feed and nourish the crops of the Nile Valley and feed the community.