= Custom dates with the Ruby Holidays Gem
  
It's easy to add your own custom holiday definitions to the Holidays gem. In a nutshell:
1. Build a definition file
2. Run the <tt>rake</tt> task to make a custom module
3. <tt>require</tt> your new module and enjoy!


== 1. Building the YAML file

Definition files have two main parts: *months* and *methods*. Before you start, you may want to look some of the existing files at http://code.dunae.ca/svn/holidays/trunk/data.

=== Months

Holidays are grouped by month from 1 through 12.  Each entry within a month can have several fields.

[<tt>name</tt>]     The name of the holiday.
[<tt>regions</tt>]  One or more region codes.

===== Dates defined by a fixed date (e.g. January 1st) 

[<tt>wday</tt>]  Integer representing day of the month (1 through 31).

For example, the following holiday is on the first of January and available in the <tt>ca</tt>, <tt>us</tt> and <tt>au</tt> regions.

    1:
    - name: New Year's Day
      regions: [ca,us,au]
      mday: 1


===== Dates defined by a week number (e.g. first Monday of a month)

[<tt>wday</tt>]  Integer representing day of the week (0 = Sunday through 6 = Saturday).
[<tt>week</tt>]  Integer representing week number (1 = first week, 3 = third week, -1 = last week),


For example, the following holiday is on the first Monday of September and available in the <tt>ca</tt> region.

    9:
    - name: Labour Day
      regions: [ca]
      week: 1
      wday: 1




=== Calculating dates with methods

In addition to defining holidays by day or week, you can create custom methods to calculate a date.

For example, Canada celebrates Victoria Day, which falls on the Monday on or before May 24.  So, under the <tt>methods</tt> section we could create a custom method that returns a Date object.

  methods:
    ca_victoria_day: |
      def self.ca_victoria_day(year)
        date = Date.civil(year,5,24)
        if date.wday > 1
          date -= (date.wday - 1)
        elsif date.wday == 0
          date -= 6
        end
        date
      end

This would be represented in the <tt>months</tt> section as:

    5:
    - name: Victoria Day
      regions: [ca]
      function: lambda { |year| ca_victoria_day(year) }


Functions called in this manner must return either a Date object or an integer representing the day of the month.



== 2. Building the definition module

Once you have your YAML definition file you need to generate a Ruby module using <tt>rake</tt>.

To build the module for school holidays

  rake generate MyCustomDates custom.yaml


Your module can include definitions from multiple YAML files.

  rake generate MyCustomDates ca.yaml us.yaml mx.yaml custom.yaml


== 3. Using your custom definitions

Your custom module is ready to use.

  require 'holidays'
  require 'path/to/custom'
  
  Holidays.by_day(date, :your_region)



=== Sharing

If you've built a definition file that others might enjoy, why not share it?

Send any definition files to 'code' at  'dunae.ca'.