DateTime s representation in milliseconds

Question

I have a SQL-server timestamp that I need to convert into a representation of time in milliseconds since 1970  Can I do this with plain SQL  If not  I ve extracted it into a DateTime variable in C   Is it possible to get a millisec representation of this    Thanks   Teja

User · Accepted Answer

You re probably trying to convert to a UNIX-like timestamp  which are in UTC   yourDateTime ToUniversalTime   Subtract      new DateTime 1970  1  1  0  0  0  DateTimeKind Utc        TotalMilliseconds   This also avoids summertime issues  since UTC doesn t have those

User · Answer

Using the answer of Andoma  this is what I m doing  You can create a Struct or a Class like this one  struct Date               public static double GetTime DateTime dateTime                        return dateTime ToUniversalTime   Subtract new DateTime 1970  1  1  0  0  0  DateTimeKind Utc   TotalMilliseconds                     public static DateTime DateTimeParse double milliseconds                        return new DateTime 1970  1  1  0  0  0  DateTimeKind Utc  AddMilliseconds milliseconds  ToLocalTime                       And you can use this in your code as following  DateTime dateTime   DateTime Now   double total   Date GetTime dateTime    dateTime   Date DateTimeParse total     I hope this help you

User · Answer

SELECT CAST DATEDIFF S   1970-01-01   SYSDATETIME    AS BIGINT    1000   This does not give you full precision  but DATEDIFF MS    causes overflow   If seconds are good enough  this should do it

User · Answer

There are ToUnixTime   and ToUnixTimeMs   methods in DateTimeExtensions class  DateTime UtcNow ToUnixTimeMs

User · Answer

This other solution for covert datetime to unixtimestampmillis C    private static readonly DateTime UnixEpoch   new DateTime 1970  1  1  0  0  0  DateTimeKind Utc    public static long GetCurrentUnixTimestampMillis         DateTime localDateTime  univDateTime      localDateTime   DateTime Now                univDateTime   localDateTime ToUniversalTime        return  long  univDateTime - UnixEpoch  TotalMilliseconds

User · Answer

In C   you can write   long  date - new DateTime 1970  1  1   TotalMilliseconds

User · Answer

As of  NET 4 6  you can use a DateTimeOffset object to get the unix milliseconds  It has a constructor which takes a DateTime object  so you can just pass in your object as demonstrated below   DateTime yourDateTime  long yourDateTimeMilliseconds   new DateTimeOffset yourDateTime  ToUnixTimeMilliseconds      As noted in other answers  make sure yourDateTime has the correct Kind specified  or use  ToUniversalTime   to convert it to UTC time first   Here you can learn more about DateTimeOffset

[c#] DateTime's representation in milliseconds?

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