Re: dua during the last third of the night...
Peace xlusively_you
Yes ... that is true.
The last third is defined by the portion of time between Sunset and Subh Sadiq. Some have interpreted the night as the time between sunset and sunrise, but this is not so strong.
The times will change over the year, they will change more rapidly and by greater amounts further away you live from the equator, either south or north.
The best time to assume prayer in the last third is about half an hour before beginning of fajr. The sort of time that you get up to eat for Suhoor during Ramadan.
12:00 am is the middle of the night for all places in the world on the two equinoxes ... in March and in September. These two are the only days when the night and day are both of equal duration and when the shadow line falls exactly parallel to the longitudinal lines.