Date and Time

The DateTime Type

• The DateTime Type C# has built-in support for dates and times

• This type can be used to represent a date and time, and it provides access to the system clock

• The type also supports many operations that can make it easy to work with dates and times

The following block demonstrates some DateTime operations:

var currentTime = DateTime.Now; // current time

var today = DateTime.Today; // current date (time is midnight)
var tomorrow = DateTime.Today.AddDays(1);
var yesterday = DateTime.Today.AddDays(-1);

var someDate = new DateTime(2016,7,1); // 1 July 2016, midnight
var someMoment = new DateTime(2016,7,1,8,0,0); // 1 July 2016, 08:00.00
var someDay = DateTime.Parse("7/1/2016");

The DateTime.Now and DateTime.Today properties are static, means you can access them without having an instance of a DateTime

Formatting Dates and Times

There are many ways to display dates and times. Times can be represented using 12-hour AM/PM style times, or using 24-hour format.

In formatting operations, custom date and time format strings can be used with the ToString method of a date and time instance.

The following example illustrates this:

using System;

class Program
{
    static void Main()
    {
        DateTime d1 =  DateTime.Today;

        Console.WriteLine("Today is " + d1.ToString("MMMM dd, yyyy"));     
        Console.WriteLine("Today is " + d1.ToString("dd/MMM/yyyy"));             
        Console.WriteLine("Today is " + d1.ToString("dd/MM/yy"));             
        Console.WriteLine("Today is " + d1.ToString("dd-MM-yy"));                 
        Console.WriteLine("Today is " + d1.ToString("dd.MM.yy"));                 
    }
}

Getting to Parts of Dates and Times

DateTime type has many properties you can use to access different individual components of the date or time, such as the month, day, year, hour, minute, etc. The following sample demonstrates some of these properties:

var someTime = new DateTime(2016,7,1,11,10,9); // 1 July 2016 11:10:09 AM
int year = someTime.Year; // 2016
int month = someTime.Month; // 7
int day = someTime.Day; // 1
int hour = someTime.Hour; // 11
int minute = someTime.Minute; // 10
int second = someTime.Second; // 9

Calculating Durations Between DateTimes

Sometimes it can be useful to think about the difference between two times, or the duration of an event. For instance, you could calculate how many days are left in the year. To do so, you would need to determine the first day of the next year, and then compare that to today. The following code shows how to do this:

DateTime nextYear = new DateTime(DateTime.Today.Year+1, 1, 1);
TimeSpan duration = nextYear - DateTime.Today;
Console.WriteLine($"There are {duration.TotalDays} days left in the year");

This produces a new type called a TimeSpan, which is used to represent a span of time, or a duration.

TimeSpan provides many ways to represent its value, the TotalDays property will show how many full days the TimeSpan includes.

Exercise

Write a program that accepts a birth date ( dd/MMM/yyyy) and calculates how many days old the person with that birth date is currently.

Hint: Use Parse() method of DateTime class

Expectation:

Enter DOB in dd/MMM/yyyy format
07/sep/2010
4187

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Enter DOB in dd/MMM/yyyy format");
        var dobString = Console.ReadLine();        
        //write your code here        
    }
}