Calculate previous week's start and end date

What is the best way to calculate the previous week's start and end date in C#? I.e. today 18 March would result in 9 March (Monday last week) and 15 March (Sunday last week).

I have seen this done with DayOfWeek and a switch statement to work out an offset but was wondering whether there is a more elegant way.

Solution 1:

You can skip the while loop and use

DateTime mondayOfLastWeek = date.AddDays( -(int)date.DayOfWeek - 6 );

This assumes you're using Monday as the first day of the week.

Solution 2:

DayOfWeek weekStart = DayOfWeek.Monday; // or Sunday, or whenever
DateTime startingDate = DateTime.Today;

while(startingDate.DayOfWeek != weekStart)
    startingDate = startingDate.AddDays(-1);

DateTime previousWeekStart = startingDate.AddDays(-7);
DateTime previousWeekEnd = startingDate.AddDays(-1);

Read: Backtrack one day at a time until we're at the start of this week, and then subtract seven to get to the start of last week.

Solution 3:

using Fluent DateTime https://github.com/FluentDateTime/FluentDateTime

var dateTime = 1.Weeks().Ago();
var monday = dateTime.Previous(DayOfWeek.Sunday);
var sunday = dateTime.Next(DayOfWeek.Sunday);

Solution 4:

Using DayOfWeek would be a way of achieving this:

    DateTime date = DateTime.Now.AddDays(-7);
    while (date.DayOfWeek != DayOfWeek.Monday)
    {
        date = date.AddDays(-1);
    }

    DateTime startDate = date;
    DateTime endDate = date.AddDays(7);