This story has been updated with background and details.

All executive departments and agencies will be closed Christmas Eve, giving federal employees a four-day weekend, President Obama declared Friday in an executive order.

Obama allowed for some exceptions to the holiday, where necessary. “The heads of executive branch departments and agencies may determine that certain offices and installations of their organizations, or parts thereof, must remain open and that certain employees must report for duty on Dec. 24, 2012, for reasons of national security, defense or other public need,” the order stated.

Employees required to work on Monday will be “entitled to pay at the rate of his basic pay, plus premium pay at a rate equal to the rate of his basic pay,” according to rules on holiday pay for federal workers.

The order does not apply to U.S. Postal Service employees. Mail will be delivered as usual Monday and post Offices will be open -- though closing early -- a USPS spokesman confirmed.

Obama’s order follows in the tradition of granting federal employees a four-day weekend when Christmas falls on a Tuesday, as it does this year. President Bush did the same in 2001 and in 2007. The announcement is typically made earlier in December, with previous orders issued Dec. 5 and 6, respectively.

This year, some federal employees attempted to force Obama’s hand, taking to an online petition to drum up support for the extra holiday. That petition recently received its 25,000th signature, passing the threshold to guarantee a response from the White House. At the time of the order, there was still no official petition response on the White House’s We the People website. The order, however, seemed to fully address the issue.

Obama gave federal employees a half day on Christmas Eve in 2009, when it fell on a Thursday and Christmas on a Friday. He did not order any extra holiday time in 2010 or 2011.