Tuesday's first of four lunar "blood moon" eclipses mark one of two earth-shaking events, depending on your viewpoint: Either a critical moment in the unfolding prophecy of the End Times, or Tax Day.
SEE MORE: KREM 2 viewers' Blood Moon pics
It could also be just a spectacularly beautiful astronomical event over the next two years.
The tetrad — or four consecutive and complete lunar eclipses occurring at approximately six-month intervals — will all be visible over the United States this year and next, according to NASA lunar eclipse expert Fred Espenak.
While Espenak sees it as a frequent and naturally occurring event, best-selling author and Texas televangelist pastor John Hagee sees the four blood moons as evidence of a future "world-shaking event" that begins to fulfill End Times prophecy.
The controversial 73-year-old founder of Texas' Cornerstone Church says he has been preparing for this tetrad for years. The preparation includes a book — Blood Moons: Something is About to Change and an online TV special Tuesday.
"What is the prophetic significance (of the four blood moons)? Is this the end of the age?" Hagee asked his congregation during a sermon shortly after his book was released, Christianity Today reports.
He cites Acts 2:19-20 as a sign: "And I will show wonders in Heaven above and signs in the Earth beneath, the sun shall be turned into darkness and the moon into blood before the coming of the great and awesome day of the Lord."
In extensive remarks available online on his interpretation of the Blood Moons, Hagee says, "I believe that the heavens are God's billboard, that He has been sending signals to planet Earth, and we just haven't been picking them up."
He adds: "God is literally screaming at the world: 'I'm coming soon.'"
A spokesman for the televangelist said tells USA TODAY on Monday that Hagee "has not associated the blood moons with the end of days."
In general, evangelicals view the End Times not as the immediate end of the world, rather as a period when certain events must unfold, according to prophecy, over a long period of time prior to the return of Jesus. Evengelicals, however, would agree that many of these End Times events -- particularly as related to Israel -- are happening now.
Hagee, who sees the tetrad as particularly meaningful for Israel, says previous tetrads, in 1492, 1948 and 1967, coincided with such events as the expulsion of Jews from Spain at the end of the Inquisition, statehood for Israel, and the Six-Day War.
NASA's Espenak does not consider tetrads as particularly rare, noting in a statement that there are nine sets of tetrads during the 21st century. He notes that there have been periods with no tetrads, notably from 1600 to 1900.
"The most unique thing about the 2014-2015 tetrad is that all of them are visible for all or parts of the USA," Espenak said in a prepared statement.
The full eclipse is known as a "blood moon" because, NASA explains, the sunset red glow that rings the Earth as it blocks the light from the sun is cast upon the moon.
The first one in this tetrad begins at 2 a.m. ET Tuesday. The other dates are Oct. 8, April 4, 2015, and Sept. 28, 2015.
In 2008, Hagee was criticized for suggesting that Hurricane Katrina was a result of God's wrath toward the city of New Orleans for planning a rally for gays and lesbians.
He later apologized for his remarks and expressed sympathy for those who suffered, saying "ultimately neither I nor any other person can know the mind of God concerning Hurricane Katrina. I should not have suggested otherwise."
NOTE: The Perot Museum in Dallas will be hosting a watch party from midnight until 3 a.m. It's free and open to all ages. Go here for more information.