Regular Expressions

We can use the gsub method on the string. gsub can be called with a regex and a block, with each match being yielded to the block where you can run arbitrary Ruby code on the match text to transform as needed.

require "date"

sample = <<-SAMPLE
The first battle was on 10/8/14,
followed by additional skirmishes
on 11/9/14 and 11/12/14.
SAMPLE

date_pattern = %r{\d+/\d+/\d+}

sample.gsub(date_pattern) do |date|
  Date.
    strptime(date, "%m/%d/%y").
    strftime("%A %b %-d")
end

The block first parses the date string, explicitly specifying the date format using strptime, then uses strftime to output the date in the preferred format.

This produces:

The first battle was on Wednesday Oct 8, followed by additional skirmishes on Sunday Nov 9 and Wednesday Nov 12.

Check out the Weekly Iteration episode on Regex, specifically the section on using gsub with regex and a block for a more detailed summary.

Note: If you want to get really fancy, you can use the ActiveSupport date.day.ordinalize method to get dates like 2nd and 4th. Check out our Weekly Iteration episode on ActiveSupport for more on ActiveSupport.