# a time xx years ago

#### benein

##### Senior Member
Hi everyone!
I have a question.
It is from one of my test.

[context]
Runoff channels on Mars speak of a time 4 billion years ago (the age of the Martian highlands), when the atmosphere was thicker, the surface warmer, and liquid water widespread.

[question]
I'm having trouble understanding the structure of the part "a time 4 billion years ago". I have a guess. I would like to hear what you think about my guess.

[my guess]
To me, the structure of "a time 4 billion years ago" resembles a structure of "a long time ago".
= [a time 4 billion years ago = a long time ago (in terms of structure)]

So my guess is that instead of 'long', the writer put '4 billion years'.
= [a 4 billion years time ago ]

And for some reason, it is not right to put '4 billion years' before 'time'. So it is moved behind 'time'
= [a time 4 billion years ago]

What do you think about my guess?

Thank you for reading my question.

• #### natkretep

##### Moderato con anima (English Only)
Yes, I think you're on the right track. Although in English, modifiers often come before the head noun (time in your example), a phrase as a modifier can come after the head noun.

So we can say a long time ago as well as a time long ago. We talk about a beautiful girl but might still say She was a girl beautiful in an ethereal way.

#### heypresto

##### Senior Member
I think you are over-complicating things. The sentence is simply saying ' . . . speak of a (period of) time (that passed) 4 billion years ago (the age of . . . '

#### benein

##### Senior Member
Thank you natkretep for the explanation and examples!
I didn't know that I can say "a time long ago". I thought it was wrong!

Please tell me know if I'm wrong.
What you mean is that both "a time 4 billion years ago" and "a4 billion years time ago" are OK.

Do I understand you correctly?

#### natkretep

##### Moderato con anima (English Only)
No, '4 billion years' is too long a phrase to be placed before ​time.

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