android – how does the DateTime.now().microsecondsSinceEpoch precisely work in dart

for (int i = 0; i < 3; i++) {
   ultimate key = DateTime.now().microsecondsSinceEpoch;
   newTickets["$phoneNumber#$key#$username#${i + 1}"] = consequence.isNotEmpty ?
                                              "${selectedType}_${consequence[i]}"
                                              : selectedType;
                                        }

I take advantage of the precise above code in two purposes, nonetheless within the first app the important thing worth is being completely different for every iteration in contrast to the second the place all the three values of the important thing are precisely the identical , I attempted to write down a loop which iterate 100 occasions and does nothing however printing the DateTime.now().microsecondsSinceEpoch the worth modifications however not in every iteration for every a number of iterations the DateTime.now().microsecondsSinceEpoch worth change as soon as , any concepts about why that is taking place ?