What does "from this day forward" mean?

Also, from this day on; from now on. Beginning today and continuing forever, as in They promised to follow instructions from this day forward, or From now on I'll do what you say. The first rather formal expression for this concept dates from about 1500. The second was used in the past tense by Thomas Hobbes in Odyssey (1675): “From that day on, centaurs and men are foes.” The last version is the most common today.