render_time.rb

# An example Jekyll Liquid tag. Utilizes the new plugin system.
#
# 1. Make a _plugins directory in your jekyll site, and put this class in a file there.
# 2. In anyone of your pages, you can use the 'render_time' liquid tag like so:
#      {% render_time %} => November 27, 2014
#
#    Or with a custom date format (format here: http://apidock.com/ruby/DateTime/strftime):
#      {% render_time %b %d, %Y at %l:%M%P %} => Nov 27, 2014 at 4:38pm

module Jekyll
  class RenderTimeTag < Liquid::Tag

    DEFAULT_FORMAT = "%B %d, %Y"

    def initialize(tag_name, text, tokens)
      super
      @format = (text && text.length > 0) ? text : DEFAULT_FORMAT
    end

    def render(context)
      Time.now.strftime(@format)
    end
  end
end

Liquid::Template.register_tag('render_time', Jekyll::RenderTimeTag)