Elegant way to calculate number of years between two dates in rails?

Question

I currently have this less-than-ideal solution:

  def years_between_dates(date_from, date_to)
    ((date_to.to_time - date_from.to_time) / 1.year.seconds).floor
  end

The calculation doesn't have to be exact (w/ leap years etc), but does need to be fairly accurate and take into account months. 3.8 years should return 3 years, hence the floor.

I am converting to_time to account for both Date, Time, and DateTime.

I can't help but think there is a more succinct way of doing the above.

To start you could get rid of the `.to_i` and `.to_f` calls. They are unnecessary. — ptd, Jan 15 '15 at 15:46
http://stackoverflow.com/questions/1904097/how-to-calculate-how-many-years-passed-since-a-given-date-in-ruby — Brad Werth, Jan 15 '15 at 15:51
@ptd why do I not need `to_f`? It is my understanding that division of two integers will return a rounded up number? — Damien Roche, Jan 15 '15 at 16:14
**If you're going to downvote, at least post a comment with why so people can learn.** — Damien Roche, Jan 15 '15 at 16:15
@Damien Roche Subtracting two times will result in a float. You are getting an int because you are calling `.to_i` on the times. — ptd, Jan 15 '15 at 16:19

Vedant Agarwala · Answer 1 · 2017-08-23T10:57:39.263

4

Seems like yours is in fact the most elegant way.

Even in the definition of distance_of_time_in_words rails has:

distance_in_minutes = ((to_time - from_time) / 60.0).round
distance_in_seconds = (to_time - from_time).round

Reference

A little better version could be:

def years_between_dates(date_from, date_to)
  ((date_to - date_from) / 365).floor
end

edited Aug 23 '17 at 10:57

answered Aug 23 '17 at 06:38

Vedant Agarwala

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oh sorry. yeah makes sense – Vedant Agarwala Aug 23 '17 at 06:56
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What if there are more than 365 leap years between date_from and date_to? – fanjieqi Jun 22 '20 at 10:32

bryanfeller · Answer 2 · 2023-06-29T18:09:31.993

4

I stumbled across this looking for something else...

Am I crazy? Can't you just do:

def years_between_dates(date_from, date_to)
  date_to.year - date_from.year
end

or if you needed it to say "years" afterwards:

def years_between_dates(date_from, date_to)
  return "#{date_to.year - date_from.year} years"
end

I see that Piioo is right, here is a revised version. But it also doesn't compensate for leap years, which would require something more elaborate. I wouldn't use this for longer periods where accuracy is key.

def years_between_dates(date_from, date_to)
  years = (date_to - date_from).to_i / 365
  return "#{years} years"
end

edited Jun 29 '23 at 18:09

answered Jun 17 '20 at 20:27

bryanfeller

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8

1

This one is better~ – fanjieqi Jun 22 '20 at 10:33
1

This guy is a true Rubyist. – Petercopter Aug 26 '20 at 05:31
7

But that's not the same as in the question. It does not consider the months or days of the year. Between 1979-10-20 and 2020-10-19 are 40 years. But on 2020-10-20 its 41. In your calculation the whole year 2020 is 41 years. – Piioo Oct 19 '20 at 10:58

score 1 · Answer 3 · edited Aug 03 '21 at 14:38

1

if you want to get the real years between two dates, you have to consider the months and days, for example if you want to get the dates between 2010-10-01 to 2021-09-09 , the real years must be 10 years. Then you can use the next function:

  def years_between_dates(since_date, until_date)
    years = until_date.year - since_date.year
    if (until_date.month < since_date.month) ||
       (until_date.month == since_date.month && until_date.day < since_date.day)
      years -= 1
    end
    years
  end

edited Aug 03 '21 at 14:38

Community

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answered Apr 23 '21 at 03:12

andres.ara

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can this condition be simplified to `until_date.month <= since_date.month && until_date.day < since_date.day`? – CaTs Mar 03 '22 at 08:11

nazar kuliyev · Answer 4 · 2022-03-31T09:37:40.240

1

Simple as:

((Time.now-1.year.ago)/1.year).abs

edited Mar 31 '22 at 09:37

answered Mar 31 '22 at 09:16

nazar kuliyev

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Elegant way to calculate number of years between two dates in rails?

4 Answers4