If there are no specific dates listed, then it's doubtful that what you have is a contract, but rather an offer letter. An offer letter is almost never legally binding, and frankly you don't want it to be. I think the chances that you are still receiving the same salary as you were in 2001 is fairly slim, for example. If an offer letter were binding, you'd never get a raise, never get additional vacation, never get any benefits not specifically mentioned in the letter. And if the terms can be changed in ways that benefit you, why should terms that don't benefit you be carved in stone? You don't get to have it both ways.