'I have eaten' is the present perfect tense of the verb 'to eat', 'I had eaten' is the past perfect and 'I will have eaten' is the future perfect.

I have eaten是动词eat的现在完成时；I had eaten是过去完成时；I will have eaten是将来完成时。

《牛津词典》

It studies these populations in the past, present and future using quantitative data and mathematical models as tools of analysis.

它使用定量数据和数学模型作为分析工具，研究这些人口在过去、现在和未来的情况。

youdao

It studies these populations, in the past, present and future, using quantitative data and mathematical models as tools of analysis.

它使用定量数据和数学模型作为分析工具，研究这些物体在过去、现在和未来的数量。

youdao

Or patients might be advised to think less about the past and more about the present and the future.

VOA: special.2010.04.13

Israel's past and present and future generations form a collective entity, Israel, that collectively assents to the covenant.

犹太人的过去，现在，未来形成了一个共同的存在，全体犹太人都赞成这个契约。

耶鲁公开课 - 旧约导论课程节选

Use this pattern whenever you want to find out about the timing of an event in the past, present, or future.

当你想知道过去、现在或者未来某件事发生的时间时，你都可以使用这个句型。

When 课堂 - SpeakingMax英语口语达人

The crest was designed to combine elements of the past, present and future of the club.

BBC: QPR unveil the club's new crest

Museums matter because they engage, they tell stories of the past, present and future.

FORBES: Innovation Relies On Hope: Notes From TEDxCLE

Now with the launch of Timeline, this past, present and future similarity is especially true.

FORBES: Bookshelves, Facebook Profiles and How We Share