Many different people may not have watch, or they don’t know the time!!
Then simply they may say: “Sorry I’m not sure”.
So your answer is not complete one!!

Its the correct one, for an idelistic condition, time is different at every point of time if questioning,
I’ll show them my watch and ask what time is this?

Yes!
That’s awesome!
But people usually don’t say the second hand value.
So u can ask two persons the same question within one minute!!
Then the answer will not differ?

Well, “I met around 7700 people from 23 different countries” — Means those people may NOT understand the language in which you ask the question. e.g. If you ask the question in English to someone who doesn’t understand English much (may be a tourist just reached from another country where English is not widely understood), he may not even understand what you asked, and may not respond the way the puzzle says. (Some of them might say ‘I don’t know English’ or ‘I didn’t understand’ or something like that.)

Read carefully the puzzle!!
“I spent the entire day there asking the same question to everyone I came across”
“everybody had a different answer to the same question.”
If they don’t understand the question, they how they answered?
If they ignored him or, simply they didn’t understand his jargon they couldn’t answer.
So everybody of course knows the speaker’s language !!!!

That logic applies to your comment to the answer given by dyj below as well. There, you counted “I’m not sure” as an answer. Then why can’t “I don’t know English” be an answer as well?  Also, what if the person whom you asked didn’t understand your style of writing the number? (Say, I could write the Numeral ‘1’ in any other script (say, Arabic or Devnagari (Hindi) or some other Indian language, which many people may not understand. On the other hand, if I wrote the number as ‘1’ as in the answer, and the person I asked happens to be someone who understands numerals in his own regional language only, he might ask, ‘oh.. is that a number?’ (Of course, the possibility may be one in a million, but you can’t rule it out since you ask ‘everyone came across’.)

“everybody had a different answer to the same question”…….How it possible?
Because everybody understands the question…Otherwise at least two of them may say : “Sorry we don’t know  English/ the answer”!

Yes , may be one of them may say: Sorry, I don’t know. But not two. Because two answer will differ.. must differ by statements!!

So you can’t argue that someone may not know the speaker’s language! They may be Arabic ,may be from India…China….But they answer differently!! so all of them understood what the speaker told then . We can guarantee here only one may don’t know the speaker’s language but, except that person all of them know that language…

Suppose I asked two Arabic people the same question .Suppose they don’t know English.They will answer:
A: Sorry I don’t know(In Arabic)
B:Sorry I don’t know (In Arabic)
But their answers don’t become different!
Now u can also argue…..One may say:
A:Sorry(In Arabic)
B:Sorry, I don’t know English(In Arabic)
The answers are different…Then I will say I’m sorry.