The Apache Software Foundation /əˈpætʃi/ (ASF) is an American nonprofit corporation (classified as a 501(c)(3) organization in the United States) to support a number of open source software projects. The ASF was formed from a group of developers of the Apache HTTP Server, and incorporated on March 25, 1999. As of 2021, it includes approximately 1000 members.

The Apache Software Foundation is a decentralized open source community of developers. The software they produce is distributed under the terms of the Apache License, a permissive open-source license for free and open-source software (FOSS). The Apache projects are characterized by a collaborative, consensus-based development process and an open and pragmatic software license, which is to say that it allows developers who receive the software freely, to re-distribute it under nonfree terms. Each project is managed by a self-selected team of technical experts who are active contributors to the project. The ASF is a meritocracy, implying that membership of the foundation is granted only to volunteers who have actively contributed to Apache projects. The ASF is considered a second generation open-source organization,in that commercial support is provided without the risk of platform lock-in.

Among the ASF's objectives are: to provide legal protection to volunteers working on Apache projects; to prevent the Apache brand name from being used by other organizations without permission.

The ASF also holds several ApacheCon conferences each year, highlighting Apache projects and related technology.
From the passage provided, extract the year Apache Software Foundation was incorporated on.
Apache Software Foundation was incorporated on March 25, 1999