Season Two
Because of a Solar flare, SG-1 travel back in time to 1969. Just before they leave General Hammond gives Sam a note.
In 1969 Cheyenne Mountain was used for missile testing, SG-1 are interrogated by the military, but give nothing away for fear of corrupting the time line. As they are transported to another facility they are set free by a Lieutenant Hammond, the future General.
In order to get back to the future the team must locate the Stargate and find a way to use it at the time of the next solar flare.
Hitching a lift with a couple of hippies they find Catherine and learn that the Stargate is in a Warehouse in Washington.
Daniel says at the time he was about 4½ years old which suggests he was born in 1965