From the founding of America, U.S. presidents have developed and used various types of presidential or executive directives. The best-known directives are executive orders and presidential proclamations—written instructions or declarations issued by the president that carry the full force of the law. These vary from formalities, such as the presidential proclamation of Earth Day or a National Day of Prayer, to orders that effect major policy changes, such as President Bill Clinton’s executive orders calling for preferential treatment in federal contracting based on race or ethnicity.