When could the U.S. default? Economists say debt ceiling "X date" coming sooner than expected

Tax season is over; revenues are down. And as the House moves to hold its first vote on legislation to address the debt limit, some new estimates put the day the federal government will run out of money to pay its bills sooner than economists initially expected.

While projections of the so-called "X date" have put it sometime over the summer, Treasury Secretary Janet Yellen said in January the U.S. would be able to avoid default through at least early June as it uses "extraordinary measures" to pay its bills.  At that time, the Bipartisan Policy Center estimated the date would likely arrive this summer or early fall. 

Economists at Bank of America expect Yellen to update her guidance on the X date by early May and anticipate she will stick with the early June estimate. But with tax revenues down, economists at multiple banks have started moving up their own estimated timelines for the threat of a default.