It takes one year for the Earth to complete one revolution around the Sun. Our calendar is based on this fact, but some planets may finish one revolution around the Sun faster than us, while other planets will take more time to do it. For example, it takes Saturn 29 years to complete one revolution around the Sun, on the meantime, the Earth will have completed 29 revolutions.
Neptune is the planet that takes longer to complete one revolution around the Sun, approximately 164.79 years, while it takes only 88 days for Mercury to complete one revolution.
