How could "00:00" = "12:00 a.m." ?

def time_converter(time):
if int(time[:2]) > 12:
    return str(str(int(time[:2]) - 12) + time[2:] + " p.m.")
elif int(time[:2]) == 12 and int(time[3:]) != 0:
    return str(time + " p.m.")
elif int(time[:2]) < 10:
    return str(time[1:] + " a.m.")
else:
    return str(time + " a.m.")

I ran my code , everything was fine , but it blocked in "00:00" convert to 12-hours.and it just showed me the answear "00:00" = "12:00 a.m." ,then i just failed... cant even solve the problem .

Could anyone help me ?