A lot of pop prophecy teachers out there think the “blood moon” or “darkening” in Joel 2:31, Matt 24:29, and the sixth seal will be able to be predicted by logging onto NASA’s website in order to forecast when some future peculiar astronomical alignment will occur such as a lunar or solar eclipse.
They are misguided and will continue to be so. I am one of the very few teachers (maybe the only one) in the Bible prophecy realm out there that have argued that the Bible indicates that this celestial phenomenon will be caused by, not some predicable astronomic alignment, but rather unpredictable atmospheric conditions. The atmospheric conditions could be caused by several factors including a super volcano, celestial dust or other objects entering the earth’s atmosphere, or a type of an oceanic storm such as the UK is experiencing right now. The “blood moon,” however, will not occur piecemeal; it will occur within a cluster of other cataclysmic events, so it will not be mistaken for another typical catastrophe. In other words, the world will know that it is from God and not merely “natural.” This is why—and how—it will function as the portend to the day of the Lord’s wrath.
All of these points are expounded in my book Antichrist Before the Day of the Lord: What Every Christian Needs to Know about the Return of Christ.