How to assess elapsed time to execute a .exe file or opening a desktop application?

[Sudershan]

I used following code but not got any success. It is not providing the elapsed time to open the pdf file. Please help with suitable code. I am using python 3.7

start = timeit()
subprocess.Popen(r'C:\Program Files (x86)\Adobe\Acrobat Reader DC\Reader\AcroRD32.exe')
end = timeit()
elapsed_time = end - start