drop function if exists easter_date;
delimiter go
create function easter_date(yr year) returns date deterministic
begin
  declare a, b, c, d, e, k, m, n, p, q int;
  declare easter date;
  set k = floor( yr / 100 );
  set a = mod( yr, 19 );
  set b = mod( yr, 4 );
  set c = mod( yr, 7 );
  set q = floor( k / 4 );
  set p = floor(( 13 + 8 * k) / 25 );
  set m = mod( (15-p+k-q), 30 );
  set d = mod( (19 * a + m), 30 );
  set n = mod( (4+k-q), 7 );
  set e = mod( (2*b+4*c+6*d+n), 7 );
  return case
    when d + e <= 9 then concat_ws('-', yr, '03', 22 + d + e)
    when d = 29 and e = 6 then concat_ws('-', yr, '04-19')
    when d = 28 and e = 6 and a > 10 then concat_ws('-', yr, '04-18')
    else concat_ws('-', yr, '04', lpad(d + e - 9, 2, 0))
  end;
end;
go
delimiter ;
select easter_date(2018);
+-------------------+
| easter_date(2018) |
+-------------------+
| 2024-04-01        |
+-------------------+