Dutch is what is called a V2 language, where the verb must be the second function in a sentence. Since adverbs can go ahead of the verb, the verb comes before the subject of the sentence so it is still in the second position. This causes the verb and subject to switch places in a process called inversion.
- ik eet nu een boterham -> Nu eet ik een boterham
This is exactly the same as the process that creates yes/no questions, and just like with yes/no questions, if the subject is je or jij, the verb loses the final -t.
Duolingo Lesson: www.duolingo.com/skill/dn/word-order-2