simple past

·Use the Simple Past to express the idea that an action started and finished at a specific time in the past. Sometimes, the speaker may not actually mention the specific time, but they do have one specific time in mind.

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Examples:
I saw a movie yesterday.
I didn't see a play yesterday.
Last year, I traveled to Japan.

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·The Simple Past can be used with a duration which starts and stops in the past. A duration is a longer action often indicated by expressions such as: for two years, for five minutes, all day, all year, etc.

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Examples:
I lived in Brazil for two years.
Shauna studied Japanese for five years.
They sat at the beach all day.

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credits:

http://www.englishpage.com/verbpage/simplepast.html