class Time

Time::DATE_FORMATS[:short_ordinal] = ->(time) { time.strftime("%B #{time.day.ordinalize}") }
Time::DATE_FORMATS[:month_and_year] = '%B %Y'
# config/initializers/time_formats.rb

or Proc instance that takes a time argument as the value.
Use the format name as the hash key and either a strftime string
You can add your own formats to the Time::DATE_FORMATS hash.
== Adding your own time formats to +to_fs+

time.to_fs(:iso8601) # => "2007-01-18T06:10:17-06:00"
time.to_fs(:rfc822) # => "Thu, 18 Jan 2007 06:10:17 -0600"
time.to_fs(:long_ordinal) # => "January 18th, 2007 06:10"
time.to_fs(:long) # => "January 18, 2007 06:10"
time.to_fs(:short) # => "18 Jan 06:10"
time.to_fs(:number) # => "20070118061017"
time.to_fs(:db) # => "2007-01-18 06:10:17"

time.to_formatted_s(:time) # => "06:10"
time.to_fs(:time) # => "06:10"

time = Time.now # => 2007-01-18 06:10:17 -06:00

This method is aliased to to_formatted_s.

Converts to a formatted string. See DATE_FORMATS for built-in formats.

def to_fs(format = :default)
  if formatter = DATE_FORMATS[format]
    formatter.respond_to?(:call) ? formatter.call(self).to_s : strftime(formatter)
  else
    # Change to `to_s` when deprecation is gone. Also deprecate `to_default_s`.
    to_default_s
  end
end