Split a number into equal parts given the number of parts
In general, building a list using a loop of the form


some_list = []
for …:
    some_list.append(…)



… would be better written using a list comprehension.

Each interval always has two elements: a start time and an end time.  These two-element lists would be better represented as tuples instead of lists.  (Tuples have a connotation that they have a fixed length, whereas lists can grow to arbitrary lengths.)

Finally, I'd package the code into a function.

def intervals(parts, duration):
    part_duration = duration / parts
    return [(i * part_duration, (i + 1) * part_duration) for i in range(parts)]