New Delhi, Aug. 1 -- For weeks, President Donald Trump was promising the world economy would change on Friday with his new tariffs in place. It was an ironclad deadline, administration officials assured the public.

But when Trump signed the order Thursday night imposing new tariffs on 68 countries and the European Union, the start date of the punishing import taxes was pushed back seven days so that the tariff schedule could be updated. The change - while potentially welcome news to countries that had not yet reached a deal with the U.S. - injected a new dose of uncertainty for consumers and businesses still wondering what's going to happen and when.

Trump has promised that his tax hikes on the nearly $3 trillion in goods imported to th...