give or take a day

[sunsunmoon]

NASA has been watching the 6-ton (5.4-metric ton) satellite closely. On Friday officials moved up their prediction for its arrival to Sept. 23, give or take a day.
(From NASA: Satellite pieces to hit Earth in a week - Yahoo! News)
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Does Sept. 23, give or take a day mean September 23, or a day before/after that day?

 

[5jj]

Does Sept. 23, give or take a day mean September 23, or a day before/after that day?

It means 'within a day either way of 23 September' - i.e., 22, 23 or 24 September.

 

[sunsunmoon]

, 5JJ.


Merriam-Webster's Learner's Dictionary
He ran a mile, give or take a few yards.
It'd be okay to say "give or take a few yards either way" instead, wouldn't it?

The movie lasted three hours, give or take a few minutes either way.
It'd be okay to say "give or take a few minutes" instead, wouldn't it?

 

[SoothingDave]

To me it's redundant to say bot "give or take" and "either way". Giving and taking tells you that the figure given may be modified slightly "either way."