Function ymd 

pub unsafe extern "C" fn ymd(year: I, month: I, date: I) -> I

Convert ymd to the number of days from 2000.01.01.

Example

use kdbplus::api::*;
use kdbplus::api::native::*;

let days=unsafe{ymd(2020, 4, 1)};
assert_eq!(days, 7396);