Obama administration officials acknowledged Monday that they made an 11th-hour change in rules for the federal health insurance exchange to allow Americans to enroll in health plans through Christmas Eve — 24 hours later than advertised — and still get coverage that begins on New Year’s Day. The switch occurred in the form of a software change that government officials and IT contractors inserted into the computer system over the weekend for the online insurance marketplace.

Anyone who finishes enrolling by 11:59 p.m. Tuesday will have insurance on Jan. 1, the first day it becomes available.