Random date in C

Question

I m looking for some succinct  modern C  code to generate a random date between Jan 1 1995 and the current date   I m thinking some solution that utilizes Enumerable Range somehow may make this more succinct

User · Answer

This is in slight response to Joel s comment about making a slighly more optimized version   Instead of returning a random date directly  why not return a generator function which can be called repeatedly to create a random date    Func lt DateTime gt  RandomDayFunc         DateTime start   new DateTime 1995  1  1        Random gen   new Random         int range     TimeSpan  DateTime Today - start   Days       return      gt  start AddDays gen Next range

User · Answer

private Random gen   new Random    DateTime RandomDay         DateTime start   new DateTime 1995  1  1       int range    DateTime Today - start  Days                 return start AddDays gen Next range        For better performance if this will be called repeatedly  create the start and gen  and maybe even range  variables outside of the function

User · Answer

Well  if you gonna present alternate optimization  we can also go for an iterator    static IEnumerable lt DateTime gt  RandomDay          DateTime start   new DateTime 1995  1  1       Random gen   new Random        int range     TimeSpan  DateTime Today - start   Days      while  true          yield return  start AddDays gen Next range                you could use it like this   int i 0  foreach DateTime dt in RandomDay          Console WriteLine dt       if    i    10          break

User · Answer

I am a bit late in to the game  but here is one solution which works fine       void Main                 var dateResult   GetRandomDates new DateTime 1995  1  1   DateTime UtcNow  100           foreach  var r in dateResult              Console WriteLine r              public static IList lt DateTime gt  GetRandomDates DateTime startDate  DateTime maxDate  int range                var randomResult   GetRandomNumbers range  ToArray             var calculationValue   maxDate Subtract startDate  TotalMinutes   int MaxValue          var dateResults   randomResult Select s   gt  startDate AddMinutes s   calculationValue   ToList            return dateResults             public static IEnumerable lt int gt  GetRandomNumbers int size                var data   new byte 4           using  var rng   new System Security Cryptography RNGCryptoServiceProvider data                         for  int i   0  i  lt  size  i                                  rng GetBytes data                    var value   BitConverter ToInt32 data  0                   yield return value  lt  0   value   -1   value

User · Answer

Well  if you gonna present alternate optimization  we can also go for an iterator    static IEnumerable lt DateTime gt  RandomDay          DateTime start   new DateTime 1995  1  1       Random gen   new Random        int range     TimeSpan  DateTime Today - start   Days      while  true          yield return  start AddDays gen Next range                you could use it like this   int i 0  foreach DateTime dt in RandomDay          Console WriteLine dt       if    i    10          break

User · Answer

Useful extension based of  Jeremy Thompson s solution public static class RandomExtensions       public static DateTime Next this Random random  DateTime start  DateTime  end   null                end     new DateTime            int range    end Value - start  Days          return start AddDays random Next range

User · Answer

Small method that returns a random date as string  based on some simple input parameters  Built based on variations from the above answers   public string RandomDate int startYear   1960  string outputDateFormat    yyyy-MM-dd        DateTime start   new DateTime startYear  1  1      Random gen   new Random Guid NewGuid   GetHashCode        int range    DateTime Today - start  Days     return start AddDays gen Next range   ToString outputDateFormat

User · Answer

Start with a fixed date object  Jan 1  1995   and add a random number of days with AddDays  obviusly  pay attention not surpassing the current date

User · Answer

I have taken  Joel Coehoorn answer and made the changes he adviced - put the variable out of the method and put all in class  Plus now the time is random too  Here is the result   class RandomDateTime       DateTime start      Random gen      int range       public RandomDateTime                 start   new DateTime 1995  1  1           gen   new Random            range    DateTime Today - start  Days             public DateTime Next                 return start AddDays gen Next range   AddHours gen Next 0 24   AddMinutes gen Next 0 60   AddSeconds gen Next 0 60              And example how to use to write 100 random DateTimes to console   RandomDateTime date   new RandomDateTime    for  int i   0  i  lt  100  i          Console WriteLine date Next

User · Answer

I am a bit late in to the game  but here is one solution which works fine       void Main                 var dateResult   GetRandomDates new DateTime 1995  1  1   DateTime UtcNow  100           foreach  var r in dateResult              Console WriteLine r              public static IList lt DateTime gt  GetRandomDates DateTime startDate  DateTime maxDate  int range                var randomResult   GetRandomNumbers range  ToArray             var calculationValue   maxDate Subtract startDate  TotalMinutes   int MaxValue          var dateResults   randomResult Select s   gt  startDate AddMinutes s   calculationValue   ToList            return dateResults             public static IEnumerable lt int gt  GetRandomNumbers int size                var data   new byte 4           using  var rng   new System Security Cryptography RNGCryptoServiceProvider data                         for  int i   0  i  lt  size  i                                  rng GetBytes data                    var value   BitConverter ToInt32 data  0                   yield return value  lt  0   value   -1   value

User · Answer

This is in slight response to Joel s comment about making a slighly more optimized version   Instead of returning a random date directly  why not return a generator function which can be called repeatedly to create a random date    Func lt DateTime gt  RandomDayFunc         DateTime start   new DateTime 1995  1  1        Random gen   new Random         int range     TimeSpan  DateTime Today - start   Days       return      gt  start AddDays gen Next range

User · Answer

Well  if you gonna present alternate optimization  we can also go for an iterator    static IEnumerable lt DateTime gt  RandomDay          DateTime start   new DateTime 1995  1  1       Random gen   new Random        int range     TimeSpan  DateTime Today - start   Days      while  true          yield return  start AddDays gen Next range                you could use it like this   int i 0  foreach DateTime dt in RandomDay          Console WriteLine dt       if    i    10          break

User · Answer

private Random gen   new Random    DateTime RandomDay         DateTime start   new DateTime 1995  1  1       int range    DateTime Today - start  Days                 return start AddDays gen Next range        For better performance if this will be called repeatedly  create the start and gen  and maybe even range  variables outside of the function

User · Answer

Useful extension based of  Jeremy Thompson s solution public static class RandomExtensions       public static DateTime Next this Random random  DateTime start  DateTime  end   null                end     new DateTime            int range    end Value - start  Days          return start AddDays random Next range

User · Answer

Well  if you gonna present alternate optimization  we can also go for an iterator    static IEnumerable lt DateTime gt  RandomDay          DateTime start   new DateTime 1995  1  1       Random gen   new Random        int range     TimeSpan  DateTime Today - start   Days      while  true          yield return  start AddDays gen Next range                you could use it like this   int i 0  foreach DateTime dt in RandomDay          Console WriteLine dt       if    i    10          break

User · Answer

Start with a fixed date object  Jan 1  1995   and add a random number of days with AddDays  obviusly  pay attention not surpassing the current date

User · Answer

I have taken  Joel Coehoorn answer and made the changes he adviced - put the variable out of the method and put all in class  Plus now the time is random too  Here is the result   class RandomDateTime       DateTime start      Random gen      int range       public RandomDateTime                 start   new DateTime 1995  1  1           gen   new Random            range    DateTime Today - start  Days             public DateTime Next                 return start AddDays gen Next range   AddHours gen Next 0 24   AddMinutes gen Next 0 60   AddSeconds gen Next 0 60              And example how to use to write 100 random DateTimes to console   RandomDateTime date   new RandomDateTime    for  int i   0  i  lt  100  i          Console WriteLine date Next

User · Answer

Start with a fixed date object  Jan 1  1995   and add a random number of days with AddDays  obviusly  pay attention not surpassing the current date

User · Answer

private Random gen   new Random    DateTime RandomDay         DateTime start   new DateTime 1995  1  1       int range    DateTime Today - start  Days                 return start AddDays gen Next range        For better performance if this will be called repeatedly  create the start and gen  and maybe even range  variables outside of the function

User · Answer

This is in slight response to Joel s comment about making a slighly more optimized version   Instead of returning a random date directly  why not return a generator function which can be called repeatedly to create a random date    Func lt DateTime gt  RandomDayFunc         DateTime start   new DateTime 1995  1  1        Random gen   new Random         int range     TimeSpan  DateTime Today - start   Days       return      gt  start AddDays gen Next range

User · Answer

Small method that returns a random date as string  based on some simple input parameters  Built based on variations from the above answers   public string RandomDate int startYear   1960  string outputDateFormat    yyyy-MM-dd        DateTime start   new DateTime startYear  1  1      Random gen   new Random Guid NewGuid   GetHashCode        int range    DateTime Today - start  Days     return start AddDays gen Next range   ToString outputDateFormat

User · Answer

This is in slight response to Joel s comment about making a slighly more optimized version   Instead of returning a random date directly  why not return a generator function which can be called repeatedly to create a random date    Func lt DateTime gt  RandomDayFunc         DateTime start   new DateTime 1995  1  1        Random gen   new Random         int range     TimeSpan  DateTime Today - start   Days       return      gt  start AddDays gen Next range

User · Answer

Start with a fixed date object  Jan 1  1995   and add a random number of days with AddDays  obviusly  pay attention not surpassing the current date

User · Answer

private Random gen   new Random    DateTime RandomDay         DateTime start   new DateTime 1995  1  1       int range    DateTime Today - start  Days                 return start AddDays gen Next range        For better performance if this will be called repeatedly  create the start and gen  and maybe even range  variables outside of the function

[c#] Random date in C#

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