Hi, a C program with this output, without using arrays, can you explain me pls?

General Well-being Log ====================== Set the year and month for the well-being log (YYYY MM): 2009 1 ERROR: The year must be between 2010 and 2021 inclusive Set the year and month for the well-being log (YYYY MM): 2022 1 ERROR: The year must be between 2010 and 2021 inclusive Set the year and month for the well-being log (YYYY MM): 2021 0 ERROR: Jan.(1) - Dec.(12) Set the year and month for the well-being log (YYYY MM): 2021 13 ERROR: Jan.(1) - Dec.(12) Set the year and month for the well-being log (YYYY MM): 2009 0 ERROR: The year must be between 2010 and 2021 inclusive ERROR: Jan.(1) - Dec.(12) Set the year and month for the well-being log (YYYY MM): 2022 13 ERROR: The year must be between 2010 and 2021 inclusive ERROR: Jan.(1) - Dec.(12) Set the year and month for the well-being log (YYYY MM): 2021 2 *** Log date set! *** 2021-FEB-01 Morning rating (0.0-5.0): -0.9 ERROR: Rating must be between 0.0 and 5.0 inclusive! Morning rating (0.0-5.0): 5.01 ERROR: Rating must be between 0.0 and 5.0 inclusive! Morning rating (0.0-5.0): 4.25 Evening rating (0.0-5.0): -0.9 ERROR: Rating must be between 0.0 and 5.0 inclusive! Evening rating (0.0-5.0): 5.01 ERROR: Rating must be between 0.0 and 5.0 inclusive! Evening rating (0.0-5.0): 5 2021-FEB-02 Morning rating (0.0-5.0): 0 Evening rating (0.0-5.0): 4.9 2021-FEB-03 Morning rating (0.0-5.0): 5 Evening rating (0.0-5.0): 0 Summary ======= Morning total rating: 9.250 Evening total rating: 9.900 ----------------------------Overall total rating: 19.150 Average morning rating: 3.1 Average evening rating: 3.3 ---------------------------- Average overall rating: 3