time # UTC time 是 Time 或者 ActiveSupport::TimeWithZone 对象
#=> 该方法只是转化了时间,没有更改时区。
8.hours.since time
#=> 该方法依赖于本地时区是北京,而我的 case 不满足
time.getlocal 或者 time.localtime
#3 楼@zlx_star
in_time_zone(zone = ::Time.zone)
Returns the simultaneous time in Time.zone.
Time.zone = 'Hawaii' # => 'Hawaii'
DateTime.new(2000).in_time_zone # => Fri, 31 Dec 1999 14:00:00 HST -10:00
This method is similar to Time#localtime, except that it uses Time.zone as the local zone instead of the operating system’s time zone.
You can also pass in a TimeZone instance or string that identifies a TimeZone as an argument, and the conversion will be based on that zone instead of Time.zone.
DateTime.new(2000).in_time_zone('Alaska') # => Fri, 31 Dec 1999 15:00:00 AKST -09:00