Kammala jumla mai zuwa: Daga 1833 zuwa 1836, Day yana aiki a Hancock Barracks, Maine kuma ya yi aiki a Fort Independence, Massachusetts a 1836. Ya yi aiki a kan aikin daukar ma'aikata a wurare daban-daban daga 1836 zuwa 1838 kuma ya shiga cikin Seminole War na 1838-1839. Day ya kamu da rashin lafiya a Florida kuma ya kasance a hutu daga 1839 zuwa 1841. Ya koma Florida a 1841 kuma ya kasance har 1842. Ya yi aiki tare da 2nd Infantry a Buffalo, New York daga 1842 zuwa 1845 da Detroit, Michigan daga 1845 zuwa 1846. Ya shiga cikin Yakin Mexico da Amurka daga 1846 zuwa 1847, yana aiki tare da Rundunar Sojoji ta 2 a matsayin wani ɓangare na Brigade David E. Twiggs kuma ya shiga cikin fadace-fadace ciki har da
Veracruz, Cerro Gordo, Contreras, Churubusco, Moline del Rey da kuma Chapultepec.