calceph_gettimespan returns always integer dates

from calcephpy import CalcephBin, Constants
import calcephpy
import math

peph = CalcephBin.open('de441_part-1.bsp')
peph.gettimespan()
peph.close()

returns (-3100015.0, 2440432.0, 1) instead of (-3100015.5, 2440432.5, 1)