Rubuta ci gaba ga wannan sakin layi - 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 Mexican-American daga 1846 zuwa 1847, yana aiki tare da 2nd Infantry a matsayin wani ɓangare na David E. Twiggs 'Brigade kuma ya shiga cikin fadace-fadace ciki har da Veracruz
, Cerro Gordo, Contreras, Churubusco, Moline del Rey da kuma Chapultepec.