This snippet of code calculates the date of the most...

This snippet of code calculates the date of the most recent Friday on or before the last day of the current month.

Here’s a detailed breakdown:

1. var daysInMonth = DateTime.DaysInMonth(now.Year, now.Month);
   This calculates the number of days in the current month.
   DateTime.DaysInMonth(year, month) is a method that returns the total number of days for a specific month in a given year.

2. var lastDay = new DateTime(now.Year, now.Month, daysInMonth);
   This creates a DateTime object representing the last day of the current month. It uses the calculated daysInMonth as the day.

3. var lastFriday = lastDay.AddDays(-(int)lastDay.DayOfWeek - 2);
   This calculates the date of the last Friday on or before the last day of the month:

   • lastDay.DayOfWeek gives the day of the week of the last day (e.g., DayOfWeek.Sunday = 0, DayOfWeek.Monday = 1, ...).
   • (int)lastDay.DayOfWeek converts the DayOfWeek enum to its corresponding integer (0 for Sunday, 1 for Monday, etc.).
   • Adding -(int)lastDay.DayOfWeek shifts back to the previous Sunday.
   • -2 then moves from Sunday to Friday.
   • Finally, the .AddDays() method adjusts the lastDay date accordingly.

Example:

If today (now) is October 2023:

• now.Year = 2023
• now.Month = 10 (October)
• The number of days in October = 31.
  So, lastDay = new DateTime(2023, 10, 31) (October 31, 2023).
• October 31, 2023, is a Tuesday (DayOfWeek.Tuesday = 2).
• (int)lastDay.DayOfWeek = 2.
• lastDay.AddDays(-(int)lastDay.DayOfWeek - 2) = lastDay.AddDays(-2 - 2) = lastDay.AddDays(-4).
  This moves back 4 days to October 27, 2023 (Friday).

Result: lastFriday contains the date of the last Friday in the current month.