A person travelling westwards sets his watch behind at each successive time zone . 一个向西旅行的人，在每个时区边界，要把他的表拨慢一小时。
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He set back his watch three minutes 他将表拨慢了三分钟。
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For example , an alarm clock that sounds a wake - up call every morning at the same time cannot simply use a fixed rate schedule of 86400000 milliseconds 24 hours , because the alarm would be too late or early on the days the clocks go forward or backward if your time zone uses daylight saving time 例如，每天清晨在同一时间发出叫醒铃声的闹钟不能简单地使用固定的计划频率86400000毫秒（ 24小时） ，因为在钟拨快或者拨慢（如果您的时区使用夏令时）的那些天里，叫醒可能过晚或者过早。
