The census here says that Oliver & Sarah have been married since 1881.

Oliver Sanders
United States Census, 1900
Name Oliver Sanders
Event Type Census
Event Year 1900
Event Place Hadley Township, Saratoga, New York, United States
Gender Male
Age 38
Marital Status Married
Race White
Race (Original) W
Relationship to Head of Household Head
Relationship to Head of Household (Original) Head
Years Married 19
Birth Date Oct 1862
Birthplace New York
Marriage Year (Estimated) 1881
Father's Birthplace New York
Mother's Birthplace New York
Household
Role
Sex
Age
Birthplace
Oliver Sanders Head M 38 New York
Sarah Sanders Wife F 48 New York
Henry Sanders Son M 18 New York
Eva Sanders Daughter F 16 New York
Freddie Sanders Son M 12 New York
Mamie Sanders Daughter F 8 New York
Leroy Sanders Son M 3 New York