CODEWITHSUNDEEP
c#.netdatetime
Ashish Ashu
Ashish Ashu

Reputation: 14677

How to compare DateTime in C#?

I don't want user to give the back date or time.

How can I compare if the entered date and time is LESS then the current time?

If the current date and Time is 17-Jun-2010 , 12:25 PM , I want user cannot give date before 17 Jun -2010 and time before 12:25 PM.

Like my function return false if the time entered by user is 16-Jun-2010 and time 12:24 PM

Upvotes: 175

Views: 366177

Answers (9)

cskwg
cskwg

Reputation: 849

using System;
//
public enum TimeUnit : byte {
    Unknown = 0x00, // 
    Nanosecond = 0x01, // ns, not available in DateTime
    Millisecond = 0x02, // ms
    Second = 0x04, // sec
    Minute = 0x08, // min
    Hour = 0x10, // h
    Day = 0x20, // d
    Month = 0x40, // M
    Year = 0x80, // Y
    AllDate = TimeUnit.Year | TimeUnit.Month | TimeUnit.Day,
    AllTime = TimeUnit.Hour | TimeUnit.Minute | TimeUnit.Second,
    UpToNanosecond = TimeUnit.Nanosecond | TimeUnit.Millisecond | TimeUnit.Second | TimeUnit.Minute | TimeUnit.Hour | TimeUnit.Day | TimeUnit.Month | TimeUnit.Year,
    UpToMillisecond = TimeUnit.Millisecond | TimeUnit.Second | TimeUnit.Minute | TimeUnit.Hour | TimeUnit.Day | TimeUnit.Month | TimeUnit.Year,
    UpToSecond = TimeUnit.Second | TimeUnit.Minute | TimeUnit.Hour | TimeUnit.Day | TimeUnit.Month | TimeUnit.Year,
    UpToMinute = TimeUnit.Minute | TimeUnit.Hour | TimeUnit.Day | TimeUnit.Month | TimeUnit.Year,
    UpToHour = TimeUnit.Hour | TimeUnit.Day | TimeUnit.Month | TimeUnit.Year,
    UpToDay = TimeUnit.Day | TimeUnit.Month | TimeUnit.Year,
    UpToMonth = TimeUnit.Month | TimeUnit.Year,
};
//
public static partial class DateTimeEx {
    //
    private static void _Compare( ref int result, int flags, TimeUnit tu, int a, int b ) {
        var which = (int) tu;
        if ( 0 != ( flags & which ) ) {
            if ( a != b ) result |= which;
        }
    }
    ///<summary>Compare Dates. The returned TimeUnit will have one flag set for every different field. It will NOT indicate which date is bigger or smaller.</summary>
    public static TimeUnit Compare( this DateTime a, DateTime b, TimeUnit unit ) {
        int result = 0;
        var flags = (int) unit;
        //ompare( ref result, flags, TimeUnit.Nanosecond, a.Nano, b.Nanosecond );
        _Compare( ref result, flags, TimeUnit.Millisecond, a.Millisecond, b.Millisecond );
        _Compare( ref result, flags, TimeUnit.Second, a.Second, b.Second );
        _Compare( ref result, flags, TimeUnit.Minute, a.Minute, b.Minute );
        _Compare( ref result, flags, TimeUnit.Hour, a.Hour, b.Hour );
        _Compare( ref result, flags, TimeUnit.Day, a.Day, b.Day );
        _Compare( ref result, flags, TimeUnit.Month, a.Month, b.Month );
        _Compare( ref result, flags, TimeUnit.Year, a.Year, b.Year );
        return (TimeUnit) result;
    }
}
public static class Tests {
    //
    private static void TestCompare() {
        var test = DateTime.UtcNow;
        var ts = test.ToUnixTimestamp( true );
        var test2 = DateTimeEx.ToDateTime( ts, true );
        var ok = 0 == DateTimeEx.Compare( test, test2, TimeUnit.UpToSecond );
        Log.Assert( ok );
        ts = test.ToUnixTimestamp( false );
        test2 = DateTimeEx.ToDateTime( ts, false );
        ok = 0 == DateTimeEx.Compare( test, test2, TimeUnit.UpToSecond );
        Log.Assert( ok );
    }
}

Upvotes: 0

Fattie
Fattie

Reputation: 12287

Here's a typical simple example in the Unity milieu

using UnityEngine;

public class Launch : MonoBehaviour
{
    void Start()
    {
        Debug.Log("today " + System.DateTime.Now.ToString("MM/dd/yyyy"));

        // don't allow the app to be run after June 10th
        System.DateTime lastDay = new System.DateTime(2020, 6, 10);
        System.DateTime today = System.DateTime.Now;

        if (lastDay < today) {
            Debug.Log("quit the app");
            Application.Quit();
        }
        UnityEngine.SceneManagement.SceneManager.LoadScene("Welcome");
    }
}

Upvotes: 0

yannick triqueneaux
yannick triqueneaux

Reputation: 121

If you have two DateTime that looks the same, but Compare or Equals doesn't return what you expect, this is how to compare them.

Here an example with 1-millisecond precision:

bool areSame = (date1 - date2) > TimeSpan.FromMilliseconds(1d);

Upvotes: 12

Dieu Phan Dinh
Dieu Phan Dinh

Reputation: 44

//Time compare.
private int CompareTime(string t1, string t2)
{
    TimeSpan s1 = TimeSpan.Parse(t1);
    TimeSpan s2 = TimeSpan.Parse(t2);
    return s2.CompareTo(s1);
}

Upvotes: 1

AlbertK
AlbertK

Reputation: 13227

In general case you need to compare DateTimes with the same Kind:

if (date1.ToUniversalTime() < date2.ToUniversalTime())
    Console.WriteLine("date1 is earlier than date2");

Explanation from MSDN about DateTime.Compare (This is also relevant for operators like >, <, == and etc.):

To determine the relationship of t1 to t2, the Compare method compares the Ticks property of t1 and t2 but ignores their Kind property. Before comparing DateTime objects, ensure that the objects represent times in the same time zone.

Thus, a simple comparison may give an unexpected result when dealing with DateTimes that are represented in different timezones.

Upvotes: 9

Majid Bajwa
Majid Bajwa

Reputation: 9

public static bool CompareDateTimes(this DateTime firstDate, DateTime secondDate) 
{
   return firstDate.Day == secondDate.Day && firstDate.Month == secondDate.Month && firstDate.Year == secondDate.Year;
}

Upvotes: -3

Sнаđошƒаӽ
Sнаđошƒаӽ

Reputation: 17612

MuSTaNG's answer says it all, but I am still adding it to make it a little more elaborate, with links and all.

The conventional operators

are available for DateTime since .NET Framework 1.1. Also, addition and subtraction of DateTime objects are also possible using conventional operators + and -.

One example from MSDN:

Equality: 
System.DateTime april19 = new DateTime(2001, 4, 19);
System.DateTime otherDate = new DateTime(1991, 6, 5);

// areEqual gets false.
bool areEqual = april19 == otherDate;

otherDate = new DateTime(2001, 4, 19);
// areEqual gets true.
areEqual = april19 == otherDate;

Other operators can be used likewise.

Here is the list all operators available for DateTime.

Upvotes: 30

MuSTaNG
MuSTaNG

Reputation: 3922

Microsoft has also implemented the operators '<' and '>'. So you use these to compare two dates.

if (date1 < DateTime.Now)
   Console.WriteLine("Less than the current time!");

Upvotes: 344

Ahmet Kakıcı
Ahmet Kakıcı

Reputation: 6404

MSDN: DateTime.Compare

DateTime date1 = new DateTime(2009, 8, 1, 0, 0, 0);
DateTime date2 = new DateTime(2009, 8, 1, 12, 0, 0);
int result = DateTime.Compare(date1, date2);
string relationship;

if (result < 0)
   relationship = "is earlier than";
else if (result == 0)
   relationship = "is the same time as";         
else
   relationship = "is later than";

Console.WriteLine("{0} {1} {2}", date1, relationship, date2);
// The example displays the following output:
//    8/1/2009 12:00:00 AM is earlier than 8/1/2009 12:00:00 PM

Upvotes: 214

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