The alignment of planets last occurred in the year 2020. Prior to that, there was 2005 and 2016.
The three concentric planets align once every 39.6 years on average. On average, the eight planets align every 396 billion years since there is a 1 in 100 raised to the 5th power probability that Mars, Jupiter, Saturn, Uranus, and Neptune are all going to be within this arc on any specific pass.