Question

I have a String 20120119 which represents a date in the format 'YYYYMMDD'.

I want to parse this string into a Ruby object that represents a Date so that I can do some basic date calculation, such as diff against today’s date.

I am using version 1.8.6 (requirement).

Answer 1

You could use the Date.strptime method provided in Ruby’s Standard Library:

require 'date'
string = "20120723"
date = Date.strptime(string,"%Y%m%d")

Alternately, as suggested in the comments, you could use Date.parse, because the heuristics work correctly in this case:

require 'date'
string = "20120723"
date = Date.parse(string)

Both will raise an ArgumentError if the date is not valid:

require 'date'
Date.strptime('2012-March', '%Y-%m')
#=> ArgumentError: invalid date

Date.parse('2012-Foo') # Note that '2012-March' would actually work here
#=> ArgumentError: invalid date

If you also want to represent hours, minutes, and so on, you should look at DateTime. DateTime also provides a parse method which works like the parse method on Date. The same goes for strptime.