The provided code calculates the date of the day immediately...

The provided code calculates the date of the day immediately before the date stored in the variable lastFriday. Here's a breakdown of what it does:

1. lastFriday: This variable is presumed to already contain a DateTime object representing a specific date (in this case, a Friday).
2. .AddDays(-1): The .AddDays() method is called on the lastFriday variable, with an argument of -1. This subtracts 1 day from the value of lastFriday.
3. lastDay: A new variable lastDay is declared to store the resulting date, which represents the day before lastFriday.

In summary, this code calculates the date of the day prior to lastFriday and stores it in the variable lastDay.