epoch

noun

1. a unit of geological time that is a subdivision of a period and is itself divided into ages

2. a period marked by distinctive character or reckoned from a fixed point or event

Synonym: era

3. (astronomy) an arbitrarily fixed date that is the point in time relative to which information (as coordinates of a celestial body) is recorded

Synonym: date of reference

1. 时代;纪元
If you refer to a long period of time as an epoch, you mean that important events or great changes took place during it.

e.g. The birth of Christ was the beginning of a major epoch of world history.
基督诞生是世界历史上一个重要纪元的开端。

2. （地质中的）世，纪，期
An epoch is a very long period of time in the earth's development, marked by particular physical or biological characteristics.

e.g. Two main glacial epochs affected both areas during the last 100 million years of Precambrian times.
在前寒武纪的最后1亿年中，两个主要的冰川时期对两个地区都产生了影响。

1. 历元：当然全天的天体中NGC天体只是一小部分,在DSS菜单里的View New Target窗口中可以自己输入赤经(Right Ascension)赤纬(Declination),天区面积(Size,角分作单位)和历元(Epoch),输入后按查看(View)就能生成所要的图像,

2. epoch的反义词

2. 新纪元：返回对话的创建时间,按照从新纪元(epoch)开始的秒数. 初始化对话锁. 无需每次都调用这个方法,仅在子类打算(intend)使用互斥锁(alternative lock)时使用. 锁住对话. 如果对话已经被其他线程/进程锁住,则等待到锁被释放(release)时.