The term 'Revolutionary Periods' refers to a time of great change and upheaval. The two crossword solutions for this term are 'Years' (5 letters) and 'SolarYears' (10 letters). Years is a unit of time that is measured in days, weeks, months, and years. SolarYears is a unit of time that is measured in the amount of time it takes for the Earth to orbit the Sun, which is approximately 365.24 days.