python print error after custom add method - python-3.x

Question

I'm trying to make a Timecode calculator using python but I don't get why the output is wrong:
class Time:
def __init__(self, hour=0, minute=0, second=0, image=0):
self.hour = hour
self.minute = minute
self.second = second
self.image = image
def __str__(self):
return "{:02d}:{:02d}:{:02d}:{:02d}".format(self.hour, self.minute, self.second, self.image)
def __add__(self, second_time):
new_time = Time()
#define image add for 24 FPS
if(self.image + second_time.image) >= 24:
self.second += 1
new_time.image = (self.image + second_time.image) - 24
else:
new_time.image = self.image + second_time.image
#define second add for 24 FPS
if(self.second + second_time.second) >= 60:
self.minute += 1
new_time.second = (self.second + second_time.second) - 60
else:
new_time.second = self.second + second_time.second
#define minutes add for 24 FPS
if(self.minute + second_time.minute) >= 60:
self.hour += 1
new_time.minute = (self.minute + second_time.minute) - 60
else:
new_time.minute = self.minute + second_time.minute
#define hours add for 24 FPS
if(self.hour + second_time.hour) >= 24:
new_time.hour = (self.hour + second_time.hour) - 24
else:
new_time.hour = self.hour + second_time.hour
return new_time
time1 = Time(2, 23, 21, 10)
time2 = Time(2, 21, 2, 22)
test = time1 + time2
print(time1)
if I print time1 before "test = time1 + time2" time1 = 02:23:21:10 but when I print it after test like in the code above the value of time 1 is 02:23:22:10...
did I miss something? why would the value of time1 change?
Thanks for your help