Hostile Mobs Spawn Too Early

There is no bug here- when the sun is setting, zombies and skeletons begin spawning under trees and overhangs and zombies can walk into the sunlight before the sun has fully set (skeletons are a bit smarter and will not do this, but can be pushed into sunlight by other mobs or environmental sources). To verify that they do not burn immediately after spawning:

1. Create a new superflat world with commands on

2. /gamerule doDaylightCycle false

3. /gamerule doMobLoot false

4. /time set 13188

5. /kill @e[type=!player]
   Observe how only slimes spawn around you

6. /time set 13189

7. /kill @e[type=!player]
   Observe that all sorts of hostile mobs spawn around you, but none burn because the sun has already gone down.