The number 120 in prophetic times
In those days Peter stood up among the brothers (a gathering of about a hundred and twenty) and said..." (Acts 1, 12-15) (120 were gathered in the upper room when the Holy Spirit came upon them)
B) Even outside of the Bible we find this 120 number being important:
1) According to Jewish understanding of history, there are 120 Jubilees. A jubilee is a 50-year Jewish time cycle that removed every man out of captivity and into his own land. 120 of these Jubilees (50 years) = 6000 years of man. See this article and this article and this book.
2) 120 members in the modern day Israeli Knesset who govern Israel.
C) Then, finally, it seems to have an important function in prophetic times:
1) If the Rapture happens in 2025, as many believe, then it is exactly 120 years after the most holy and morally transforming revival in history, the Welsh revival 1904-1905, began to fade when its leader Evan Roberts got mentally ill. "During the latter part of 1905, Evan Roberts was suffering increasingly from nervous exhaustion." (See this article)
2) If the Rapture happens in 2025, then it is exactly 120 years after the beginning of the maybe biggest revival in history, albeit not so holy as the Welsh revival, namely the Pentecostal Revival. It is not easy to decide exactly when it began, because Charles F. Parham, the father of Pentecostalism, began a revival with speaking in tongues already in 1901 ("On January 1, 1901, the very first Pentecostal revival to take place on American soil happened just on the outskirts of Topeka, Kansas".) (see also this article). But my guess is that the revival began to become Pentecostal when William J. Seymour became involved. William J. Seymour was the Afro-american who ignited the fire of pentecost on Azusa Street. He and Charles Parham probably met during the summer 1905 in Houston, exactly when the Welsh revival began to fade, and exactly 120 years before the alleged Rapture. On July 10th 1905 Parham arrived in Houston (which in 1900 had a population of only 44 633 persons), and began mass meetings there, which were non-denominational, and surely Seymour attended one of these already in the summer, so small was the city by then. Later this year Seymour would attend a Bible School led by Parham.
3) If the Rapture happens 2025 and the Second Coming of Jesus seven years later, in passover 2032 (28 March is Easter Sunday by then), as many believe, then the passover 2032 is almost exactly 120 years after the sinking of Titanic, which also happened around passover, namely on April 15, 1912. Easter Sunday 1912 was on April 7th.