So, I've been doing some inspecting of tapx source on GitHub and from what I've seen, it does not have inherent support of parsing seconds:
from tapx-datefield Date#parseDate
function:
...
return new Date(y, m, d, hr, min, 0);
while the Date object has the following ctor:
var d = new Date(year, month, day, hours, minutes, seconds, milliseconds);