Convert Rails timezone based on browser.

timezone_cookie.js

function setCookie(key, value) {
  var expires = new Date();
  expires.setTime(expires.getTime() + (1 * 24 * 60 * 60 * 1000));
  document.cookie = key + '=' + value + ';expires=' + expires.toUTCString();
}

function getCookie(cname) {
  var name = cname + "=";
  var ca = document.cookie.split(';');
  for(var i = 0; i < ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') {
      c = c.substring(1);
    }
    if (c.indexOf(name) == 0) {
      return c.substring(name.length, c.length);
    }
  }
  return "";
}

if(!getCookie('app_timezone')) {
  var current_time = new Date();
  setCookie('app_timezone', current_time.getTimezoneOffset())
}

tz_concern.rb

module TzConcern
  extend ActiveSupport::Concern

  included do
    before_action :set_timezone
  end

  private
  def set_timezone
    min = request.cookies["app_timezone"] || -480 # if nil set offset of malaysia
    TZConverter.timezone = ActiveSupport::TimeZone[-min.to_i.minutes].try(:name)
  end
end

tz_converter.rb

module TZConverter
  thread_mattr_accessor :timezone
end

TZConverter.timezone = 'UTC'

module Date::TimezoneConverter
  def in_tz timezone=nil
    timezone ||= TZConverter.timezone
    timezone = timezone.nil? ? "Kuala Lumpur" : timezone
    self.try(:in_time_zone, timezone)
  end

  def to_tz format="%I:%M %p"
    in_tz.try(:strftime, format)
  end

  def minutes_since_midnight
    (self.hour * 3600 + self.min * 60) / 60
  end
end

module String::TimezoneConverter
  def to_utc
    timezone = TZConverter.timezone.nil? ? "Kuala Lumpur" : TZConverter.timezone
    ActiveSupport::TimeZone[timezone].parse(self)
  end
end

module Integer::TimezoneConverter
  def to_time meridian: false
    time = "%02d:%02d" % [self/60%60, self%60]
    meridian.present? ? Time.parse(time).strftime("%I:%M %p") : time
  end
end


DateTime.include Date::TimezoneConverter
Time.include Date::TimezoneConverter
String.include String::TimezoneConverter
Integer.include Integer::TimezoneConverter