"This is the first time" and "For the first time"

[Odessa Dawn]

Good point. The second sentence with 'have' seems similar to these:

100 GOLDEN GRAMMAR RULES
(By the one and only Michael Swan)

42. Use the present perfect with This is the first time … etc.
This is the first time I’ve been here. (NOT This is the first time I’m here.)
This is the fifth cup of coffee I’ve drunk today. (NOT This is the fifth cup of coffee I drink today.)

Golden Grammar Rules - EnglishmaniA
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Yang Li: What are you up to?
Finn: Well, it's quite exciting really. I've just entered the blogosphere for the first time!

More: Learning English - The English We Speak - Language of the blogosphere

English grammar rules say that with "This is the first time" we have to use present perfect. Question: Does the same rule apply to "For the first time?"

From my point of view, "This is the first time" and "For the first time" are interchangeable, aren’t they? As a result, they go with present perfect. Would you enlighten me? Am I right?
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Thank you,
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[Raymott]

Yang Li: What are you up to?
Finn: Well, it's quite exciting really. I've just entered the blogosphere for the first time!

More: Learning English - The English We Speak - Language of the blogosphere

English grammar rules say that with "This is the first time" we have to use present perfect. Question: Does the same rule apply to "For the first time?"

From my point of view, "This is the first time" and "For the first time" are interchangeable, aren’t they? As a result, they go with present perfect. Would you enlighten me? Am I right?
​

Thank you,
​

Yes, you use present perfect with both.
No, the phrases aren't interchangeable. One is a complete sentence and the other is a prepositional phrase without a verb.

 

[5jj]

From my point of view, "This is the first time" and "For the first time" are interchangeable, aren’t they? As a result, they go with present perfect. Would you enlighten me? Am I right?

No.

Last year, I ate sushi for the first time.
I am watching a ballet at the moment, and I am enjoying the experience for the first time in my life.
My mother is going to see her great granddaughter for the first time tomorrow.

You could not replace 'for the first time' with 'this is the first time' in any of those sentences.