你可以给邮件设定一个过期日期和时间，过期之后即使是收件人也无法打开或者阅读邮件。

You can define an expiration date and time for the message, after which the recipient will no longer be able to open or view it.

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委员会应为所有不同研究小组设定时间和日期，制定一个参与者、主持人和协作平台相配套的计划安排。

The committee should set times and dates for all the different study circles, and develop a plan for matching study circle partici-pants, facilitators, and sites.

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这些标记称为EXIF元数据，是为了说明照片的曝光度和光圈设定，有的相机还会显示GPS信息，当然，还有拍照的时间和日期。

These tags, called EXIF metadata, specify things like the exposure and f-stop settings, gps information if your camera has it, and, of course, the time and date the photo was taken.

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