The translation of Google translator is wrong, but also »Es ist einundzwanzig Uhr dreiundvierzig.« is a wired way to write the time. Nobody writes it that way, and maybe that's why Google never has learned to translate such a sentence and now has to guess and guessed it wrong.

This is how you speak it:

Es ist einundzwanzig Uhr dreiundvierzig.
It's nine forty-three pee-em.

But this is how you write it:

Es ist 21:43 Uhr.
It's 9:43 p.m.

Translating machines are made to translate written texts. And that's why the Google translator outputs a sentence that is grammatically correct in written English, but it had troubles to understand a sentence that is a literal transcription of a spoken sentence.

I could reproduce Google's error, but I also fed Google with the correct written sentence, and it correctly translated it into »It's 9:43 p.m.« Then I tried DeepL, which I think is a more powerful translator than than provided by Google, and I got these results:

So, both translators have troubles processing the transcription of the spoken version. Google gave an answer that is wrong, but DeepL tried the best to translate it correctly and it still tried to provide a translation that is stylistic as close to the input, as possible.

The translation by Google Translate is wrong, but also »Es ist einundzwanzig Uhr dreiundvierzig.« is a weird way to write the time. Nobody writes it that way, and maybe that's why Google has never learned to translate such a sentence; now has to guess and it guessed wrong.

This is how you speak it:

Es ist einundzwanzig Uhr dreiundvierzig.
It's nine forty-three pee-em.

But this is how you write it:

Es ist 21:43 Uhr.
It's 9:43 p.m.

Translating machines are made to translate written texts. And that's why the Google translator outputs a sentence that is grammatically correct in written English, but it has trouble understanding a sentence that is a literal transcription of a spoken sentence.

I could reproduce Google's error, but I also fed Google with the correct written sentence, and it correctly translated it into »It's 9:43 p.m.« Then I tried DeepL, which I think is a more powerful translator than that provided by Google, and I got these results:

So, both translators have trouble processing the transcription of the spoken version. Google gave an answer that is wrong, but DeepL tried its best to translate it correctly, and it still provided a translation that is stylistic as close to the input as possible.