distance_of_time_in_words | Better distance of time in words for Rails | Application Framework library

ActiveSupport::Duration calculates its value using the following constants and algorithm (I have added the explanation on what it's doing below but here is a link to the source). As you can see below, the SECONDS_PER_YEAR constant is the average number of seconds in the gregorian calendar (which is then used to define SECONDS_PER_MONTH). It is because of this, "average definition" of SECONDS_PER_YEAR and SECONDS_PER_MONTH that you are getting the unexpected hours, minutes and seconds. It is defined as an average because a month and year is not a standard fixed amount of time.