The ottomans fully subdued all of serbia in 1459 (It was a slow and piecemeal conquest by vassalising lords a little at a time, but this is the official date for all of serbia.) And gained its independence in 1815, though only partly, for full independence two years would have to pass. So, we're looking at 356 years, with some argument for wriggle room, such as some parts of serbia being conquered earlier, and the unrest in serbia in general during the early 19th century.