A total lunar eclipse on April 15 was the first off four such events that will occur before the end of 2015. This tetrad series of eclipses is being heralded by some religious leaders as a sign of great changes coming, with a few calling the events a sign of the end times. 

Blood moon is one of the names given to the red coloration of the moon, produced by sunlight refracting through the atmosphere of the Earth. Often, this moniker is given to eclipses where the color of the moon is dark red, like blood. But, the hue of our planetary companion is dependent on numerous factors, including weather conditions around the world. This makes true "blood moons" impossible to predict. 

The shadow produced by our home planet has two regions -- the darker inner core, called the "umbra," which is surrounded by a larger region called the penumbra, which causes the red coloration. 

John Hagee, founder of the Cornerstone Church in San Antonio, Texas, recently wrote a book claiming the tetrad of eclipses is a sign of "great changes" coming to the world. 

The last time a similar series of eclipses occurred was in the year 2003-2004. Tetrads will also occur seven more times during the 21st century.

Hagee quotes Acts 2:20, which says "The sun shall be turned into darkness, and the moon into blood, before the great and notable day of the Lord."

On April 15, the lunar eclipse coincided with the first day of Passover, and the traditional annual Seder meal. The next three eclipses in the series also coincide with Jewish holidays. The next eclipse will take place on Oct. 8, during Sukkot, the Feast of Tabernacles. In 2015, eclipses on April 4 and Sept. 28 will occur during the same festivals. 

Hagee claims God sends messages to humans by using the moon and other celestial bodies. 

"Just as in biblical times, God is controlling the sun, the moon, and the stars to send our generation a signal that something big is about to happen," the pastor wrote on his Web site. 

In ancient times, fortune tellers and mystics often believed comets were the sign of great changes, including signaling the apocalypse. Astronomers now know comets are just large balls of ice and rock orbiting the sun. 

"The most unique thing about the 2014-2015 tetrad is that all of them are visible for all or parts of the USA," Fred Espenak, NASA eclipse expert, said. 

This latest claim of the end of times is likely to be as accurate as every other claim of the end of the world throughout history.