Time Zone

类方法：

[]

all

create & new

find_tzinfo

seconds_to_utc_offset

us_zones

zones_map

实例方法：

<=>
=~

at

formatted_offset

local
local_to_utc

now

parse

period_for_local
period_for_utc

to_s

today
tomorrow
next_day
yesterday
prev_day

utc_offset

utc_to_local