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Most people know April 15 as the deadline for submitting personal tax returns, but this is not always the case.

When the date falls on a weekend, it is often moved to the following Monday. However, for the 2016 deadline, the Internal Revenue Service has given taxpayers until April 18 to pay their taxes, but it is not because the due date falls on a weekend – April 15 is a Friday.

Instead, the IRS is observing a holiday that is usually only observed in Washington, DC. Emancipation Day marks the day that the Compensated Emancipation Act was signed by President Abraham Lincoln and is observed on April 16.

Emancipation Day is a legal holiday in DC, and public employees are given the day off work. However, because April 16, 2016, falls on a Saturday, it is celebrated on the closest weekday, which is Friday April 15.

This means that public employees such as those that work for the IRS will have April 15 off of work, and so it pushes the tax deadline to April 18, a Monday, which is the next business day.

For taxpayers who live in Maine or Massachusetts, another holiday pushes their tax deadline back to Tuesday April 19. This legal holiday is Patriots’ Day, and it is always observed on the third Monday of April.

However, because residents of these states submit payment to states where April 18 is not a legal holiday, they still must pay the first installment of any estimated income tax payments by April 18.

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