Senate Minority Leader Chuck Schumer (D-NY) (C) and other Senate Democrats hold portraits of constituents affected by the government shutdown on the steps of the U.S. Capitol in Washington, U.S., January 16, 2019. Yuri Gripas | Reuters

The partial government shutdown dragged into its 27th day Thursday, leaving 800,000 workers without pay, airport security delayed and national parks largely unattended. Those effects and others will only widen if the longest-ever U.S. funding lapse lingers. No deal to reopen the government is in sight as President Donald Trump demands more than $5 billion to fund his proposed border wall and Democrats deny his request.

Going forward, federal workers could miss more paychecks and people who receive government assistance for food and housing may lose it. The shutdown will continue to delay some economic reports and could even disrupt tax returns. Here are some of the key upcoming dates to watch if nine federal departments, or about a quarter of the government, remain closed:

Jan. 20: Deadline to make early food stamp payments

Americans who rely on food stamps will still receive their benefits for February. States have to distribute those benefits on or before Jan. 20.

Jan. 25: Workers start missing next paychecks

About 800,000 federal workers started missing paychecks on Jan. 11, forcing many to scramble to figure out how to pay bills and eat. If the shutdown lingers, U.S. employees will face even more hardship. The next round of missed paydays will start on Jan. 25.

Jan. 25: Judicial agency expected to run out of money

The Administrative Office of the U.S. Courts, which supports the federal court system, is set to run out of funds on Jan. 25, according to reports. Without this funding, federal courts would keep functioning, but they would operate with only some of their usual employees.

Jan. 28: IRS expected to start accepting tax filings

The Internal Revenue Service plans to start accepting tax returns on Jan. 28, as scheduled. The Trump administration says the closure will not affect tax returns. The IRS plans to recall tens of thousands of furloughed workers for the task, and they temporarily will not get paid.

Jan. 29: State of the Union

Trump is set to give the annual State of the Union address to Congress on Jan. 29. On Wednesday, House Speaker Nancy Pelosi urged him to reschedule the remarks or give them to lawmakers in writing. Trump then told Pelosi he is postponing her planned trip overseas. Homeland Security Secretary Kirstjen Nielsen has said her department is "fully prepared to support and secure the State of the Union."

Jan. 30: GDP report

It is unclear whether the government can release the planned fourth-quarter and full-year 2018 gross domestic product report later this month. Earlier this week, a Bureau of Economic Analysis official told CNBC that "there is no way for us to know until we get back and evaluate all the various data sources that go into the advance estimate of GDP." The shutdown has already delayed release of other key economic indicators, such as retail sales, housing starts and business inventories.

Feb. 8: Third missed paycheck

This date would start the third missed pay cycle for federal workers if the shutdown remains unresolved.

Feb. 14: Key date for IPO hopefuls

A more prolonged shutdown could hurt companies such as Uber and Lyft that hope to file for initial public offerings this year. They are currently not getting the guidance from the Securities and Exchange Commission that companies aiming to go public would expect. If the closure lasts past Feb. 14, they have to provide updated, audited 2018 financial information, according to reports.

Feb. 22: Fourth missed payday

U.S. employees would miss their fourth paychecks if the closure lasts this long.

March 1: Key trade deadline

The United States and China hope to get through high-stakes trade talks and strike a new deal by March 1. The shutdown could complicate things. The Office of the U.S. Trade Representative is expected to have only about 30 percent of its staff during the closure.

Ongoing: TSA, immigration courts, food inspections