what's the meanig of
what''s the meaning of span time? could you please give me an example?

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knowlton's answer is perfect. 
You also have wingspan - which is the distance from tip to tip across a birds wings.
Life span - how long you life - and also how long you have before food goes bad.
"Spanning" meaning starting from one place in time and ending (or currently reaching) another by a certain time or distance.
The plains of Africa span for hundreds of miles.

etc "From here to there" in time or distance.

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span time = period of time

Example - Chinese history spans over 4,000 years.

Span is often used for longer amounts of time.

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a span of time = a period of time

You can modify it by saying "a LONG span of time" or "a SHORT span of time."