Manipulating DateTime values is one of the most common operations in any application. Have we ever asked ourselves how to extract the quarter of a given date value in C#? In this article, we are going to understand how we can derive the quarter and financial quarter from a given date in C#.

To download the source code for this article, you can visit our GitHub repository.

Let’s begin. 

Different Ways to Calculate the Quarter of a Given Date in C#

We can use different strategies to accomplish our goals.

Support Code Maze on Patreon to get rid of ads and get the best discounts on our products!
Become a patron at Patreon!
Tip: In scenarios where we intend to perform a large number of calculations especially, we should consider using the DateOnly structure (.NET 6+) for calculations like these that don’t require time-of-day, as it uses less memory.

Let’s explore some of them.

Use Selection to Get the Quarter of a Given Date

First, we can use selection to calculate the quarter of a given date:

public static int CalculateQuarterUsingSelection(DateTime inputDate)
{
    if (inputDate.Month <= 3)
    {
        return 1;
    }

    if (inputDate.Month <= 6)
    {
        return 2;
    }

    if (inputDate.Month <= 9)
    {
        return 3;
    }

    return 4;
}

Here, we use the DateTime.Month property to extract the month of the given date and use if statements to determine its quarter. We can also use a switch statement to accomplish the same objective.

Array Lookup Technique

Besides that, we can store the quarters in an array and perform lookup operations to determine the quarter of a given date:

public static int CalculateQuarterUsingArrayLookUp(DateTime inputDate) 
{
    int[] quarters = { 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4 };

    return quarters[inputDate.Month - 1];
}

We store the quarter values in an array and return them when we have the month of a given date. 

Division Technique for Quarter Calculations

Another method to find the quarter of a date is that we can divide the DateTime.Month property by three and use the Math.Ceiling() method to round up the result to the next full integer:

return (int)Math.Ceiling(inputDate.Month / 3.0);

We can further simplify the solution through direct integer division:

return (inputDate.Month + 2) / 3;

Use LINQ to Get the Quarter of a Given Date

Finally, we can leverage LINQ to retrieve the quarter from a given date in C#. Let’s implement an example to learn how it works:

return Enumerable.Range(1, 4).First(q => inputDate.Month <= q * 3);

Here, we use Enumerable.Range() to create a sequence of numbers from one to four, representing the four quarters. Next, we apply a predicate function to each quarter and return the first element that satisfies the condition. In this case, we use the function q => inputDate.Month <= q * 3 to check whether the inputDate.Month is less than or equal to the quarter multiplied by three and returns the quarter’s value if true. 

Note that LINQ-based methods will generally be less efficient due to the overhead of the method calls and delegates. 

Time Zones and Leap Years

Leap years do not directly affect quarter calculations; they add an extra day to February. However, since we calculate the quarter based on months, the extra day still falls in February.

We can verify that when given a leap year date and a non-leap year date, we return the same quarter:

var leapYearDate = new DateTime(2024, 2, 29);
var quarterLeapYear = CalculateQuarterMethods.CalculateQuarter(leapYearDate);
var nonLeapYearDate = new DateTime(2023, 2, 28);
var quarterNonLeapYear = CalculateQuarterMethods.CalculateQuarter(nonLeapYearDate);

Assert.AreEqual(quarterLeapYear, quarterNonLeapYear);

Likewise, time zones affect the time of a given date and, hence, have a minimal effect on quarter calculations. Therefore, converting dates into common time zones or UTC is advisable to avoid inconsistencies. 

How to Get the Start and End of Quarter Dates

Sometimes, we may want to retrieve a given quarter’s start and end dates. Let’s implement an example to demonstrate how we can achieve our goal:

public struct QuarterRange
{
    public DateTime StartQuarterDate { get; set; }
    public DateTime EndQuarterDate { get; set; }

    public QuarterRange(DateTime startQuarterDate, DateTime endQuarterDate)
    {
        StartQuarterDate = startQuarterDate;
        EndQuarterDate = endQuarterDate;
    }
}

public static QuarterRange CalculateQuarterDates(DateTime inputDate)
{
    var quarter = (int)Math.Ceiling(inputDate.Month / 3.0);
    var startQuarterMonth = (quarter - 1) * 3 + 1;
    var endQuarterMonth = startQuarterMonth + 2;
    var daysInMonth = DateTime.DaysInMonth(inputDate.Year, endQuarterMonth);
    var startQuarterDate = new DateTime(inputDate.Year, startQuarterMonth, 1);
    var endQuarterDate = new DateTime(inputDate.Year, endQuarterMonth, daysInMonth);

    return new QuarterRange (startQuarterDate, endQuarterDate);
}

Here, we define a struct QuarterRange with the start and end of quarter dates. Next, we implement a function CalculateQuarterDates() that accepts a date as a parameter.

The first step is to calculate the quarter from the given inputDate and calculate the first month of that quarter.  For example, if the input date is the 30th of December 2023, the first month of that quarter is (4 – 1) * 3 + 1 = 10.

Next, we calculate the last month of the quarter by adding two to startQuarterMonth. Finally, we set the start date to the first day of startQuarterMonth and the end of the quarter date as the last date of endQuarterMonth, which we get from the DateTime.DaysInMonth() method. Our solution can prove that the start and end of quarter dates for the fourth quarter are the 1st of October and the 31st of December, respectively. 

How to Get the Fiscal Quarter of a Given Date in C#

Sometimes, we may want to get the fiscal quarter of a given date in C#. A fiscal calendar is a range of dates that defines a company’s annual reporting cycle, which may be different from the normal calendar year.

Let’s learn how to calculate the fiscal quarter from a given date, assuming the fiscal quarter starts from the 1st of April every year:

return (int)Math.Ceiling(inputDate.Month / 3.0 + 2) % 4 + 1;

For example, if the value  inputDate is the 12th of December, (12 / 3.0 + 2) = 6. The remainder from 6 % 4 is 2; hence, the result is 3. 

However, in most cases, organizations have different fiscal calendars to suit their operational needs.

Let’s implement an example that accommodates this business need:

public static int CalculateFiscalQuarterOffset(DateTime inputDate, DateTime fiscalYearStart)
{
    var monthOffset = inputDate.Month - fiscalYearStart.Month;

    if (inputDate.Month == fiscalYearStart.Month
        && inputDate.Day < fiscalYearStart.Day
        || inputDate.Month < fiscalYearStart.Month)
    {
        monthOffset--;
    }

    monthOffset = (monthOffset + 12) % 12;
    var quarter = (monthOffset / 3) + 1;

    return quarter;
}

First, we subtract their DateTime.Month components to calculate the month offset between the given date and the fiscal year start date. Second, we check if the inputDate falls before the fiscal year start date within the same calendar year and decrease monthOffset if true. Third, we ensure that monthOffset ranges from 0 to 11 by adding 12 and getting the remainder after dividing by 12. It ensures that the result is a non-negative integer representing the number of months between the fiscal year start month and the input month. 

Finally, we calculate the quarter by dividing the normalized monthOffset by 3 and adding 1 to it. 

Conclusion 

In this article, we learn how to calculate the quarter of a given date in C#. Are there any favorite techniques of yours that we missed? Let us know in the comments section below. 

Liked it? Take a second to support Code Maze on Patreon and get the ad free reading experience!
Become a patron at Patreon!