class ActiveSupport::TimeZone

def country_zones(country_code)

for time zones in the country specified by its ISO 3166-1 Alpha2 code.
A convenience method for returning a collection of TimeZone objects 
def country_zones(country_code)
  code = country_code.to_s.upcase
  @country_zones[code] ||=
    TZInfo::Country.get(code).zone_identifiers.map do |tz_id|
      name = MAPPING.key(tz_id)
      name && self[name]
    end.compact.sort!
end