There are many reasons to mark the calendar until George W. Bush officially turns the Oval Office over to Barack Obama.

Among the best is Obama's opportunity to overturn some of Bush's worst executive orders. Where to begin: Stem-cell research ban? Gone. Drilling in environmentally sensitive areas of Utah? Not a chance. Guantanamo? Close it as soon as possible.

One reason Bush became so overwhelmingly unpopular in his last term of office was his arrogant assertion of presidential authority through executive orders intended to bypass Congress.

To his credit, Obama said in his campaign that if he were elected, he would have his attorney general review all of Bush's uses of executive powers with a special eye to those that "trample on liberty."

Rescinding the ban on stem-cell research would be a fitting first act for Obama. It would signify the sort of dramatic change in approach that Obama heralds; it would offer hope to millions of Americans who suffer from devastating diseases. And it would be welcomed by most Americans.

Obama shouldn't wait long to stop the federal Bureau of Land Management from opening about 360,000 acres in Utah to oil and gas drilling.

The president-elect's transition chief, John Podesta, told reporters Sunday that Obama regards the acreage as too environmentally fragile to support drilling.

Closing Guantanamo will be a taller order. Obama will have to decide what to do with the terrorist suspects housed there and figure out how to deal with future detainees. Guantanamo presents the darkest blot on America's image, both at home and abroad, during Bush's presidency.

At least two other Bush executive orders call for immediate reversal. The first, Bush's insistence that health workers teach abstinence only as a policy for combating AIDS in the developing world, has been partly responsible for millions of deaths in Africa. It's ludicrous that health organizations that accept U.S. funding are prevented from allowing their workers to offer potentially lifesaving condoms to men and women throughout Africa.

Closer to home, Obama also should grant California the authority to regulate carbon-dioxide emissions from automobiles.

American voters clearly said on Election Day that they want the new president to enact change when he takes office. Reversing Bush's worst presidential executive orders is the quickest way to begin accomplishing that goal.