A more thorough explanation:

A Year 2000 Warranty, also known as a Y2K Warranty, is a guarantee that software, hardware, or a product with computer components will work properly on and after January 1, 2000. These warranties were common in the late 1990s when there was concern that computer systems would not be able to handle the change from the 20th to the 21st century.

• A computer manufacturer offers a Year 2000 Warranty on their new line of desktop computers, ensuring that they will function properly after the turn of the millennium.
• A software company provides a Y2K Warranty for their accounting software, assuring customers that it will accurately handle dates and calculations beyond December 31, 1999.

These examples illustrate how a Year 2000 Warranty is a promise made by companies to their customers that their products will not be affected by the Y2K bug, which was a concern at the time. The warranties were meant to ease fears and provide assurance that computer systems would continue to function properly after the year 2000.