ok so on survival mode i went to the nether and it was mid day. then after a short while, i returned to the overworld. it was nearly night, so i ran back to my house. it started to get lighter. i read in a minecraft book that when you are in the nether in single player mode, time pauses in the overworld.

how to reproduce:

1. enter the nether at dusk.

2. set a timer for 5 minutes. 

3. exit the nether. 

4. you should be able to see a change in time.