How to Calculate Relative Time in C#

When working with dates and times in C#, you may find the need to express how much time has passed since a certain event. This can enhance user experience by displaying time in an easily digestible format, such as “2 hours ago” or “a month ago”. In this post, we will explore how to implement this functionality using the DateTime and TimeSpan classes in C#.

The Concept of Relative Time

Relative time refers to expressing the time elapsed since a certain event in terms of easily understandable language. Instead of showing exact timestamps, displaying time like “3 days ago” or “yesterday” makes it easier for users to comprehend the time elapsed without requiring them to perform mental calculations.

Implementing Relative Time in C#

Here’s how to calculate relative time using a DateTime value in C#:

Step 1: Define Constants for Time Intervals

First, you’ll need to establish constants that represent various time intervals. This makes your code cleaner and more understandable.

const int SECOND = 1;
const int MINUTE = 60 * SECOND;
const int HOUR = 60 * MINUTE;
const int DAY = 24 * HOUR;
const int MONTH = 30 * DAY;

Step 2: Calculate the TimeSpan

To determine how much time has passed, calculate the TimeSpan between the current time and the given DateTime.

var ts = new TimeSpan(DateTime.UtcNow.Ticks - yourDate.Ticks);
double delta = Math.Abs(ts.TotalSeconds);

Step 3: Determine the Appropriate Time Format

With the TimeSpan calculated, you can now determine how to format the relative time by using conditional statements.

Here’s how you can return the appropriate string based on different intervals:

if (delta < 1 * MINUTE)
    return ts.Seconds == 1 ? "one second ago" : ts.Seconds + " seconds ago";

if (delta < 2 * MINUTE)
    return "a minute ago";

if (delta < 45 * MINUTE)
    return ts.Minutes + " minutes ago";

if (delta < 90 * MINUTE)
    return "an hour ago";

if (delta < 24 * HOUR)
    return ts.Hours + " hours ago";

if (delta < 48 * HOUR)
    return "yesterday";

if (delta < 30 * DAY)
    return ts.Days + " days ago";

if (delta < 12 * MONTH)
{
    int months = Convert.ToInt32(Math.Floor((double)ts.Days / 30));
    return months <= 1 ? "one month ago" : months + " months ago";
}
else
{
    int years = Convert.ToInt32(Math.Floor((double)ts.Days / 365));
    return years <= 1 ? "one year ago" : years + " years ago";
}

Final Thoughts

The above code snippet allows you to effectively calculate and display the relative time in a straightforward manner. When you implement this in your C# application, you can improve its usability by making date references more relatable to the users.

Now you are equipped with a practical way to enhance your application with relative time displays. Happy coding!