Mark your calendars: Next year, Tax Day falls on April 18.

The IRS said Tuesday taxpayers in most states will get an extra three days to file their federal returns. The deadline is being delayed because the District of Columbia will celebrate Emancipation Day on April 15.

By law, local holidays in the nation’s capital impact tax deadlines the same way federal holidays would. Emancipation Day marks the date when President Abraham Lincoln signed into law a bill ending slavery in the District of Columbia.

Lincoln signed the bill on April 16, 1862, more than eight months before he signed the Emancipation Proclamation, which eventually led to all slaves being freed.

Next year, April 16 falls on a Saturday, so the city is celebrating the holiday on April 15.

(AP)