'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》

There are those who say "I think it will be better if we use the future and not the present tense."

还有些人说：“我认为使用将来时，而不是现在时会更好一些。”

youdao

A Spanish verb has six present-tense forms, and six each in the preterite, imperfect, future, conditional, subjunctive and two different past subjunctives, for a total of 48 forms.

西班牙语的动词现在时有六种形态，过去时、未完成时、将来时、条件句、虚拟句以及另外两种过去时虚拟式也各自有六种形态，加起来一共是48种。

youdao

So can be changed slightly, depending on tense, past, present or future as well as whether or not you want to ask a question.

因此这个句型要根据不同的时态，如过去时、现在时和将来时，作出一点调整；另外也会根据是否是问句而略有不同。

There is 课堂 - SpeakingMax英语口语达人

"You notice I'm speaking in the present tense ... because that's where all your future prayers are going to come in, " she wrote.

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