How to compare DateTime in C

Question

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

User · Answer

In general case you need to compare DateTimes with the same Kind   if  date1 ToUniversalTime    lt  date2 ToUniversalTime        Console WriteLine  date1 is earlier than date2      Explanation from MSDN about DateTime Compare  This is also relevant for operators like  gt    lt      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

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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   gt  TimeSpan FromMilliseconds 1d

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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  amp  which                   if   a    b   result    which                          lt summary gt Compare Dates  The returned TimeUnit will have one flag set for every different field  It will NOT indicate which date is bigger or smaller  lt  summary gt      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

User · Answer

public static bool CompareDateTimes this DateTime firstDate  DateTime secondDate        return firstDate Day    secondDate Day  amp  amp  firstDate Month    secondDate Month  amp  amp  firstDate Year    secondDate Year

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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  greater than   gt    less than   lt    equality       and more  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

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Microsoft has also implemented the operators   lt   and      So you use these to compare two dates   if  date1  lt  DateTime Now     Console WriteLine  Less than the current time

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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  lt  today                Debug Log  quit the app                Application Quit                      UnityEngine SceneManagement SceneManager LoadScene  Welcome

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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  lt  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

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Time compare  private int CompareTime string t1  string t2        TimeSpan s1   TimeSpan Parse t1       TimeSpan s2   TimeSpan Parse t2       return s2 CompareTo s1

[c#] How to compare DateTime in C#?

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