The emergence of new moboubs day and night

Good afternoon everyone! I have only one question. What parameters do you need to specify a mob, or in RandomSpawn parameters, that the desired mobs would appear both day and night. So far, I can only do at night. Because the base of the mob is the ZOMBIE type, but if I even change the basis for any animal (pig, cow, etc.), then the monsters are only trying to appear (ie, their appearance at the spawn point, and immediately disappears). Help)

The emergence of new moboubs day and night