Hello, I have written a c++ program using operator within multiple classes , but after running the code in code::blocks this error pops up (the screenshot of the error is attached along with the code)

ns\src\People.cpp |6| error: no matching function for call to 'Birthday::Birthday()'|

in this program People uses Birthday class information but we have also an operator running in People.cpp
having issue in using operator within multiple classes-error-jpgexamplecode.txt