On my database, the dates are stored as days elapsed since/before 01/01/1970 which I understand to be a unix date format. eg. today is 23rd May 2018 and the value is 17674

I'm trying to run a select statement against a column in a date table to show only the year. 


If I run this: 
    datepart(year, c.cko_date)

I get dates that are in the 1940s (they should be the last couple of years)

when I run 
    select datepart(year, getdate()) 
it correctly tells me the date is 2018.

Any suggestions about what I'm doing wrong?