Abeir-toril (Ah-BEER Tor-RILL), more commonly called Toril, is the name of the orb that Faerûn and the Forgotten Realms are set upon, just as Earth is the orb that Eurasia is set upon.
The name is archaic, meaning cradle of life, and is rarely used in everyday speech. Abeir-Toril is the third planet from the Sun in Realmspace; an Earth-sized planet, with an equatorial circumference of about 25,000 miles (40,000 kilometers). Its polar circumference was slightly smaller, at approximately 24,900 miles (40,100 kilometers). It is dominated by a large continent in its northern hemisphere as well as a number of other large landmasses scattered about its surface. This northern continent is called Faerûn in the west, Kara-Tur in the east, and Zakhara in the south.
Toril is orbited by one moon named Selûne (also the name of the goddess of the night sky and navigation). This luminous, heavenly body is followed in its path across the sky by a collection of shining shards, called the Tears of Selûne. These tears are said to be nothing more than a cluster of ordinary asteroids and debris that trail the moon in its path, yet the Tears remain reflective and bright even when the moon is new in the sky.
In addition to the moon, there are seven visible planets that wander against the star-misted sky. All follow regular paths around the sun. These stars are distant and eternal, and form themselves into patterns and constellations that each culture names according to its own desires.
Finally, A Torillian year is 365 days of 24 hours each. An orbit of Selûne is roughly 30 days plus five days that fall between months. These days are special occasions. Leap year is retained purely for social convenience, and provides a sixth special day that is used as the basis for long-term agreements and such contracts and activities.
Months are subdivided into three ten-day periods. These are known variously as eves, tendays, weeks, or rides throughout the Forgotten Realms.
In marking the years, the common reference to this measurement is called Dalereconing (DR). Dalereckoning is taken from the year that humans were first permitted by the Elven Court to settle in the more open regions of the forests.
I run in person and online games set in the Forgotten Realms campaign setting. Currently using the 2014 version of 5E the initial campaign starts in The Year of the Gauntlet 1367 DR