This question was here for other languages, so let here be one for Ruby.
How do I calculate number of complete years that have passed from a given date? As you probably have guessed, that's to calculate person's age automatically. The closest one is distance_of_time_in_words
Rails helper, so the following template
Jack is <%= distance_of_time_in_words (Time.now, Time.local(1950,03,22)) %> old.
yields
Jack is over 59 years old.
But I need more precise function that yields just number. Is there one?
If there exists some kind of Ruby on Rails helper function for this, this is OK, although pure 开发者_开发百科Ruby solution would be better.
Edit: the gist of the question is that a non-approximate solution is needed. At the 2nd of March Jack should be 59 years old and the next day he should be 60 years old. Leap years and such should be taken into account.
Do you want age as people typically understand it, or are you looking for a precise measure of time elapsed? If the former, there is no need to worry about leap years and other complications. You simply need to compute a difference in years and reduce it if the person has not had a birthday yet this year. If the latter, you can convert seconds elapsed into years, as other answers have suggested.
def age_in_completed_years (bd, d)
# Difference in years, less one if you have not had a birthday this year.
a = d.year - bd.year
a = a - 1 if (
bd.month > d.month or
(bd.month >= d.month and bd.day > d.day)
)
a
end
birthdate = Date.new(2000, 12, 15)
today = Date.new(2009, 12, 14)
puts age_in_completed_years(birthdate, today)
require 'date'
def years_since(dt)
delta = (Date.today - Date.parse(dt)) / 365
delta.to_i
end
I have a gem/plugin called dotiw that has a distance_of_time_in_words_hash
that will return a hash like: { :years => 59, :months => 11, :days => 27 }
. From that you could work out if it's near a certain limit.
An approach that handles leap years
Whenever you're calculating elapsed years since a date, you have to decide how to handle leap year. Here is my approach, which I think is very readable, and is able to take leap years in stride without using any "special case" logic.
def years_completed_since(start_date, end_date)
if end_date < start_date
raise ArgumentError.new(
"End date supplied (#{end_date}) is before start date (#{start_date})"
)
end
years_completed = end_date.year - start_date.year
unless reached_anniversary_in_year_of(start_date, end_date)
years_completed -= 1
end
years_completed
end
# No special logic required for leap day; its anniversary in a non-leap
# year is considered to have been reached on March 1.
def reached_anniversary_in_year_of(original_date, new_date)
if new_date.month == original_date.month
new_date.day >= original_date.day
else
new_date.month > original_date.month
end
end
I came up with the following, based on a similar reasoning as @FMc
First, compute the diff between today's year and birthday's year. Then, sum it to birthday and check the resulting date: if it's greater than today, decrease diff by 1.
To be used in Rails apps as it relies on ActiveSupport
's years
method
def age(birthday, today)
diff = today.year - birthday.year
(birthday + diff.years > today ) ? (diff - 1) : diff
end
Same idea as FM but with a simplified if statement. Obviously, you could add a second argument instead of using current time.
def age(birthdate)
now = DateTime.now
age = now.year - birthdate.year
age -= 1 if(now.yday < birthdate.yday)
age
end
withing http://github.com/radar/dotiw
Jack is <%= distance_of_time_in_words (Time.now, Time.local(1950,03,22)) %> old.
produce
Jack is 60 years old
you can use the ruby gem adroit-age
It works for leap years also..
age = AdroitAge.find_age("23/01/1990")
Update
require 'adroit-age'
dob = Date.new(1990,1,23)
or
dob = "23/01/1990".to_date
age = dob.find_age
#=> 23
I think this will always work, even for someone with a birthday near a leap day:
require 'date'
def calculate_age(start_date, end_date)
end_date.year - start_date.year - ((end_date.month > start_date.month || (end_date.month == start_date.month && end_date.day >= start_date.day)) ? 0 : 1)
end
puts calculate_age( Date.strptime('03/02/1968', '%m/%d/%Y'), Date.strptime('03/02/2010', '%m/%d/%Y'))
The calculated age with this method in the example call above is 42, which is correct despite 1968 being a leap year and the birthday being near a leap day.
Plus, this way there is no need to create a local variable.
How about this:
def age_in_years(date)
# Difference in years, less one if you have not had a birthday this year.
today = Date.today
age = today.year - date.year
age = age - 1 if [date.day, date.month, today.year].join('/').to_date > Date.today
end
d2.year - d1.year - (d2.month > d1.month || (d2.month == d1.month && d2.day >= d1.day) ? 0 : 1)
How about something like:
def years_diff(from_time,to_time)
(((to_time - from_time).abs)/ (365 * 24 * 60 * 60)).to_i
end
years_diff(Time.now,Time.local(1950,03,22)) #=> 59
years_diff(Time.now,Time.local(2009,03,22)) #=> 0
years_diff(Time.now,Time.local(2008,03,22)) #=> 1
To calculate number of Years and Months between two dates, I used this function
def calculate_year_month(from_date, to_date)
num_days = (from_date - to_date).to_i
num_months = (num_days / 30)
num_years = (num_months / 12)
num_months = (num_months % 12)
return num_years.to_s + " year(s) and " + num_months.to_s + " month(s)"
end
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