Mob Spawning

What I expected to happen was...:
Mobs like zombies, skeletons and crepers should spawn at the night in normal dificulty on the map (no in caves).

What actually happened was...:
Mobs don't appear at night on the map.

Steps to Reproduce:
1. Make a new survival map.
2. Stay in a place far from spawn area some game days.
3. Mobs don't spawn in the nearby zone.