It was 30 days until the next New Moon would appear on April 18, 1844, which was the first New Moon after the Vernal Equinox, starting the Biblical month of Abib, making October 22, 1844 the true Biblical Day of Atonement!

It hasn't happened since 1844

The exact same situation that happened in 1844 will happen again in 2007!  The Day of Atonement will be October 22, and is a month later than in Jerusalem because the New Moon will again be seen in America the night before the Equinox, but in Jerusalem the night after. Could it be the end of the Investigative Judgment?