What does this expression mean: 'ahead of his time'? Thank you!

[Kelly S.]

Test No. incompl/advan-14 "Time Expressions (2)", question 5

His invention showed that he understood what was going to happen in the future and proved he was ......... of his time.

(a) in front
(b) before
(c) ahead
(d) forward

Test No. incompl/advan-14 "Time Expressions (2)", answer 5

His invention showed that he understood what was going to happen in the future and proved he was ahead of his time.

Correct answer: (c) ahead

Your answer was: incorrect
His invention showed that he understood what was going to happen in the future and proved he was in front of his time.
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I cann't really make the sentence up, why we can not use in front. As I know, in front means to face with sth.
Please enlighten me in this sentence, Thanks a lot.

[Alan]

This expression means that he was progressive and always did things before other people had thought of the idea. In a sense it's a sort of opposite of behind the times.
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English as a Second Language
You can read my ESL story Colour Idioms

[St?phanie]

Hi, my question is not about the answer, I am just wonderring what the difference is between 'ahead of his time' and 'being ahead of time'. Does it mean the same thing? Can we put the his away anytime we want?

[Mister Micawber]

.
Two different idioms, Stephanie.

Ahead of one's time = in advance of current ideas
Ahead of time = early; before the scheduled time

Leonardo da Vinci was ahead of his time in many fields.
My wife gets irritated when I am ready to go out ahead of time.
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Native English teacher at Mister Micawber's