How do you convert epoch time in C

Question

How do you convert Unix epoch time into real time in C    Epoch beginning 1 1 1970

User · Answer

Since  Net 4 6 and above please use DateTimeOffset Now ToUnixTimeSeconds

User · Answer

UPDATE 2020 You can do this with DateTimeOffset DateTimeOffset dateTimeOffset   DateTimeOffset FromUnixTimeSeconds epochSeconds   DateTimeOffset dateTimeOffset2   DateTimeOffset FromUnixTimeMilliseconds epochMilliseconds    And if you need the DateTime object instead of DateTimeOffset  then you can call the DateTime property DateTime dateTime   dateTimeOffset DateTime    Original answer I presume that you mean Unix time  which is defined as the number of seconds since midnight  UTC  on 1st January 1970  private static readonly DateTime epoch   new DateTime 1970  1  1  0  0  0  DateTimeKind Utc    public static DateTime FromUnixTime long unixTime        return epoch AddSeconds unixTime

User · Answer

convert datetime to unix epoch seconds public static long ToUnixTime DateTime date        var epoch   new DateTime 1970  1  1  0  0  0  DateTimeKind Utc       return Convert ToInt64  date ToUniversalTime   - epoch  TotalSeconds       Should use ToUniversalTime   for the DateTime object

User · Answer

If you are not using 4 6  this may help Source  System IdentityModel Tokens           lt summary gt          DateTime as UTV for UnixEpoch          lt  summary gt      public static readonly DateTime UnixEpoch   new DateTime 1970  1  1  0  0  0  0  DateTimeKind Utc             lt summary gt          Per JWT spec          Gets the number of seconds from 1970-01-01T0 0 0Z as measured in UTC until the desired date time           lt  summary gt           lt param name  datetime  gt The DateTime to convert to seconds  lt  param gt           lt remarks gt if dateTimeUtc less than UnixEpoch  return 0 lt  remarks gt           lt returns gt the number of seconds since Unix Epoch  lt  returns gt      public static long GetIntDate DateTime datetime                DateTime dateTimeUtc   datetime          if  datetime Kind    DateTimeKind Utc                        dateTimeUtc   datetime ToUniversalTime                       if  dateTimeUtc ToUniversalTime    lt   UnixEpoch                        return 0                     return  long  dateTimeUtc - UnixEpoch  TotalSeconds

User · Answer

You actually want to AddMilliseconds milliseconds   not seconds  Adding seconds will give you an out of range exception

User · Answer

With all credit to LukeH  I ve put together some extension methods for easy use   public static DateTime FromUnixTime this long unixTime        var epoch   new DateTime 1970  1  1  0  0  0  DateTimeKind Utc       return epoch AddSeconds unixTime      public static long ToUnixTime this DateTime date        var epoch   new DateTime 1970  1  1  0  0  0  DateTimeKind Utc       return Convert ToInt64  date - epoch  TotalSeconds       Note the comment below from CodesInChaos that the above FromUnixTime returns a DateTime with a Kind of Utc  which is fine  but the above ToUnixTime is much more suspect in that doesn t account for what kind of DateTime the given date is  To allow for date s Kind being either Utc or Local  use ToUniversalTime   public static long ToUnixTime this DateTime date        var epoch   new DateTime 1970  1  1  0  0  0  DateTimeKind Utc       return Convert ToInt64  date ToUniversalTime   - epoch  TotalSeconds       ToUniversalTime will convert a Local  or Unspecified  DateTime to Utc   if you dont want to create the epoch DateTime instance when moving from DateTime to epoch you can also do     public static long ToUnixTime this DateTime date        return  date ToUniversalTime   Ticks - 621355968000000000    10000000

User · Answer

I use following extension methods for epoch conversion   public static int GetEpochSeconds this DateTime date                TimeSpan t   DateTime UtcNow - new DateTime 1970  1  1           return  int t TotalSeconds         public static DateTime FromEpochSeconds this DateTime date  long EpochSeconds                var epoch   new DateTime 1970  1  1  0  0  0  DateTimeKind Utc           return epoch AddSeconds EpochSeconds

User · Answer

Use the method DateTimeOffset ToUnixTimeMilliseconds    It returns the number of milliseconds that have elapsed since 1970-01-01T00 00 00 000Z      This is only supported with Framework 4 6 or higher   var EPOCH   DateTimeOffset UtcNow ToUnixTimeMilliseconds      It s well documented here DateTimeOffset ToUnixTimeMilliseconds  The other way out is to use the following  long EPOCH   DateTime UtcNow Ticks - new DateTime 1970  1  1 0 0 0 0  Ticks    To get the EPOCH with seconds only you may use    var Epoch    int  DateTime UtcNow - new DateTime 1970  1  1  0  0  0  DateTimeKind Utc   TotalSeconds    and convert the Epoch to DateTime with the following method  private DateTime Epoch2UTCNow int epoch         return new DateTime 1970  1  1  0  0  0  DateTimeKind Utc  AddSeconds epoch

User · Answer

If you want better performance you can use this version   public const long UnixEpochTicks   621355968000000000  public const long TicksPerMillisecond   10000  public const long TicksPerSecond   TicksPerMillisecond   1000      MethodImpl MethodImplOptions AggressiveInlining   public static DateTime FromUnixTimestamp this long unixTime        return new DateTime UnixEpochTicks   unixTime   TicksPerSecond       From a quick benchmark  BenchmarkDotNet  under net471 I get this number           Method       Mean       Error      StdDev   Scaled   --------------  ---------  ----------  ----------  -------            LukeH   5 897 ns   0 0897 ns   0 0795 ns     1 00         MyCustom   3 176 ns   0 0573 ns   0 0536 ns     0 54     2x faster against LukeH s version  if the performance mater    This is similar to how DateTime internally work

User · Answer

In case you need to convert a timeval struct  seconds  microseconds  containing UNIX time to DateTime without losing precision  this is how   DateTime  epochTime   new DateTime 1970  1  1  0  0  0  DateTimeKind Utc   private DateTime UnixTimeToDateTime Timeval unixTime        return  epochTime AddTicks          unixTime Seconds   TimeSpan TicksPerSecond           unixTime Microseconds   TimeSpan TicksPerMillisecond 1000

User · Answer

Here is my solution   public long GetTime         DateTime dtCurTime   DateTime Now ToUniversalTime         DateTime dtEpochStartTime   Convert ToDateTime  1 1 1970 0 00 00 AM         TimeSpan ts   dtCurTime Subtract dtEpochStartTime        double epochtime       epochtime         ts Days   24    ts Hours    60    ts Minutes    60    ts Seconds           return Convert ToInt64 epochtime

User · Answer

currently you can simply use DateTimeOffset UtcNow ToUnixTimeMilliseconds    it will be returned as a 64-bits long

User · Answer

The latest version of  Net  v4 6  just added built-in support for Unix time conversions  That includes both to and from Unix time represented by either seconds or milliseconds    Unix time in seconds to DateTimeOffset      DateTimeOffset dateTimeOffset   DateTimeOffset FromUnixTimeSeconds 1000      DateTimeOffset to Unix time in seconds      long unixTimeStampInSeconds   dateTimeOffset ToUnixTimeSeconds       Unix time in milliseconds to DateTimeOffset      DateTimeOffset dateTimeOffset   DateTimeOffset FromUnixTimeMilliseconds 1000000      DateTimeOffset to Unix time in milliseconds      long unixTimeStampInMilliseconds  dateTimeOffset ToUnixTimeMilliseconds        Note  These methods convert to and from DateTimeOffset  To get a DateTime representation simply use the DateTimeOffset DateTime property   DateTime dateTime   dateTimeOffset UtcDateTime

User · Answer

To not worry about using milliseconds or seconds just do       public static DateTime  ToDateTime this long unixEpochTime                DateTime epoch   new DateTime 1970  1  1  0  0  0  DateTimeKind Utc           var date   epoch AddMilliseconds unixEpochTime            if  date Year  gt  1972              return date           return epoch AddSeconds unixEpochTime           If epoch time is in seconds then there is no way you can pass year 1972 adding milliseconds

[c#] How do you convert epoch time in C#?

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