I think the e in de sounds like in the English word me, while det sounds like the English word day. It took me a while to start hearing this as well, or maybe the text-to-speech engine just got better over time and added this nuance at some point.
I've seen from other translations that using words indicating a future time in combination with a present tense verb basically equates to the future tense in other languages. Is there anything incorrect about the following answer?
"They will begin tonight."