Daylight Savings Time History. Spring Forward/Fall Back Time Change for Farmers?

What is the real story behind the Daylight Savings Time change? When does the time change? When is daylight savings time change? Was it originally designed so the farmers could work in the fields with more daylight? Was it for the revolutionary war? Why are we still doing it in 2012?
Did Benjamin Franklin really invent it? I always heard it was so the farmers could have more hours of sunlight to plow the fields, but what is the real truth?