Duration between two dates in Ruby (Rails)

Question

If I have a specific date and then add a duration to it resulting in another date

For example:

d1 = Date.parse('1996-02-17')
d2 = d1 + 67.years + 3.months # 2063-05-17

Then, how can I get the difference between those dates back (in years and months in this case), because if I do something like

ActiveSupport::Duration.build(d2.to_time - d1.to_time)

then it produces 67 years, 2 months, 4 weeks, 20 hours, 5 minutes, and 24.0 seconds. I could try rounding it off etc, but that seems messy.

I don't necessarily have to use Duration for this. Is there any way to add/subtract spans of time in Ruby on Rails in such a way that the addition and subtraction are each other's inverse?

Answer 1

I initially accepted Nitesh's answer, but found that it was buggy in other instances, e.g. for dates

d1 = Date.parse('1996-02-17')
d2 = Date.parse('2063-05-16')

which should be one day short of 67 years and 3 months, and therefore 67 years and 2 months.

To fix it, also take the days into account:

d1 = Date.parse('1996-02-17')
d2 = d1 + 67.years + 3.months - 1.days

years = d2.year - d1.year
months = d2.month - d1.month
days = d2.day - d1.day

# Adjust if d2's month is before d1's month
if months < 0
  years -= 1
  months += 12
end

months -= 1 if days < 0

puts "#{years} years and #{months} months"