preposition
BAD : She is getting married within a few hours and she feels a bit nervous.
GOOD : She is getting married in a few hours and she feels a bit nervous.
BAD : My examinations are within two weeks' time.
GOOD : My examinations are in two weeks' time.
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within = before the end of the stated period: 'The parcel should be arriving within the next five days.' 'Within six years of joining the company he was Managing Director.'
in = at the end of the stated period: 'The doctor wants to see me again in a week's time.' 'Don't go away. I'll be back in a few minutes.'