Millions of people rely on the federal health insurance marketplace to buy health care. But with open enrollment upon us, most people don’t know when they’re allowed to sign up.

A new Policygenius survey asked a nationally representative sample of 1,500 people when open enrollment for 2019 takes place. Only 21.2 percent got the right answer: Nov. 1 through Dec. 15.

The survey is based on responses from a nationally representative group of 1,501 adults across the U.S. It was conducted on Google Surveys between Oct. 1 and Oct. 4.

No One Knows When Open Enrollment Takes Place

Knowledge of open enrollment seems to have slipped from last year: 24 percent of people knew the right dates in the 2017 Policygenius survey, and a smaller share of people (21.2 percent) know when open enrollment is this year, though the dates are the same.

Members of both political parties weren’t aware of the correct dates.

Only 18.5 percent of Republicans knew when the enrollment dates were, compared to 23.7 percent of Democrats.

The most common incorrect answer was Oct. 15 through Dec. 31, which more than 30 percent of respondents chose. This may be because Medicare open enrollment starts Oct. 15, but only runs through Dec. 7.

People who receive government health insurance through programs like Medicare or Medicaid were the least likely to know when enrollment for the marketplace takes place. However, among people without any health insurance, who are the target audience for federal health insurance, only 19.7 percent knew the correct open enrollment dates.

Knowledge of the exchanges may have slipped because the Trump administration slashed the advertising budget for the federal marketplace from $100 million to $10 million.

Open Enrollment 2019

For most people who don’t get health care through an employer, spouse or government program, the marketplace open enrollment period is the only time they can sign up for health coverage for 2019. People who experience life events like moving, getting married, having a baby, or losing health coverage may qualify for a special enrollment period.

Some state exchanges have longer open enrollment periods. For example, open enrollment for California’s exchange runs from Oct. 15 through Jan. 15.

Check our state-by-state guide to open enrollment to find out when to sign up.

Graphic by Hanna Horvath.

This article originally appeared on Policygenius.