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System Profiler > Hardware Overview will give you your model ID. Finding the year out from that will take about 12 seconds on Google.
 

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The serial number contains the week and year of manufacture. The year is the 3rd digit, and the week is the 4th and 5th digit. My unibody MacBook begins with W8916..., which means my computer was manufactured the 16th week of this year.
 
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