Hebrew calendar (astronomically called a lunar conjunction and, in Hebrew, a molad) is the moment at which the sun and moon are aligned horizontally with respect to a north-south line (technically, they have the same ecliptical longitude). The period between two new moons is a synodic month. The actual length of a synodic month varies from about 29 days 6 hours and 30 minutes (29.27 days) to about 29 days and 20 hours (29.83 days), a variation range of about 13 hours and 30 minutes. Accordingly, for convenience, a long-term average length, identical to the mean synodic month of ancient times (also
April 2015 lunar eclipse 17 October 1529 (which lasted 1 minute and 42 seconds). Another shortest occurs on December 28 1917, lasting (11 minutes and 58 seconds). The next very short lunar totality will occur on 26 May 2021 (which will last 14 minutes and 24 seconds). This was the sixth total lunar eclipse out of nine with totality under 5 minutes in a five millennium period between 2,000 BC and 3,000 AD. However, due to the oblateness of the Earth, this lunar eclipse may have actually been (barely) a partial eclipse. This eclipsed moon was 12.9% smaller in apparent diameter than the supermoon