C Example Code for Calculating Day of the Week by Date

This example uses the Kim Larson formula to calculate the day of the week in the future based on the date:

First, look at the definition of Kim Larson's calculation formula in Baidu Encyclopedia:

Kim Larson calculation formula

W= (d+2*m+3* (m+1)/5+y+y/4-y/100+y/400) mod 7

In the formula, d represents the number of days in a date, m represents the number of months, and y represents the number of years.

Note: There is a difference between the formula and other formulas:

January and February are regarded as 103 and 104 months of the previous year. For example, if it is 2004-1-10, it will be converted into 2003-13-10 to be substituted into the formula.

1. Client (called by ajax):

$.get('CaculateWeekDay', { y: 2016, m: 8, d: 9 }, function (result) {
alert(result);
})

2. Server side:

/// <summary>
///  Calculate the day of the week for a specific date 
/// </summary>
/// <param name="y"> Year </param>
/// <param name="m"> Month </param>
/// <param name="d"> Day </param>
/// <returns></returns>
public string CaculateWeekDay(int y, int m, int d) 
{
if (m == 1 || m == 2) 
{
m += 12;
y--;
}
int week = (d + 2 * m + 3 * (m + 1) / 5 + y + y / 4 - y / 100 + y / 400) % 7;
string weekstr = "";
switch (week)
{
case 0: weekstr = " Week 1"; break;
case 1: weekstr = " Week 2"; break;
case 2: weekstr = " Week 3"; break;
case 3: weekstr = " Week 4"; break;
case 4: weekstr = " Week 5"; break;
case 5: weekstr = " Week 6"; break;
case 6: weekstr = " Week 7"; break;
}
return weekstr;
}