I can get you some C++ source code that will allow you to add or subtract a number of days to a given date and return the correct date. I have a high knowledge of MATLAB, Simulink, and Arduino/Raspberry Pi. Also, having a good knowledge of PLC programming (LD), GUI, Python, C++. Also, I have experience with the following non-technical computer programs, such as Microsoft Office, Adobe Photoshop, Unity. Besides that, I am a great enthusiast and a quick learner.