The Spanish-American war lasted from April 25, 1898 to August 12, 1898 (when the ceasefire was signed), which is 110 days. The formal treaty ending the war was signed about four months later.
The length of the 1990 Gulf War depends on when you consider it to have started - on August 2 when Iraq invaded Kuwait, or on 15 January when the UN ultimatum was not met, or on 17 January when full-scale warfare began. The latter dates give it a length of 43-45 days before the end of hostilities on 28 February. The earlier date makes it much longer.