How to convert Milliseconds to date format in C#?

Question

In C# how can I convert Unix-style timestamp to yyyy-MM-ddThh:mm:ssZ?

Solution 1

Start by converting your milliseconds to a TimeSpan:

var time = TimeSpan.FromMilliseconds(milliseconds);

Now, in .NET 4 you can call .ToString() with a format string argument. See http://msdn.microsoft.com/en-us/library/system.timespan.tostring.aspx

In previous versions of .NET, you'll have to manually construct the formatted string from the TimeSpan's properties.

Solution 2

new DateTime(numTicks * 10000)

The DateTime(long ticks) constructor is what you need. Each tick represents 100 nanoseconds so multiply by 10000 to get to 1 millisecond.

Solution 3

If the milliseconds is based on UNIX epoch time, then you can use:

var posixTime = DateTime.SpecifyKind(new DateTime(1970, 1, 1), DateTimeKind.Utc);
var time = posixTime.AddMilliseconds(milliSecs);

Solution 4

This worked for me:

DateTimeOffset.FromUnixTimeMilliseconds(milliseconds);

You can get just the DateTime from that if you need it.

Solution 5

Here you go:

public static class UnixDateTime
    {
        public static DateTimeOffset FromUnixTimeSeconds(long seconds)
        {
            if (seconds < -62135596800L || seconds > 253402300799L)
                throw new ArgumentOutOfRangeException("seconds", seconds, "");

            return new DateTimeOffset(seconds * 10000000L + 621355968000000000L, TimeSpan.Zero);
        }

        public static DateTimeOffset FromUnixTimeMilliseconds(long milliseconds)
        {
            if (milliseconds < -62135596800000L || milliseconds > 253402300799999L)
                throw new ArgumentOutOfRangeException("milliseconds", milliseconds, "");

            return new DateTimeOffset(milliseconds * 10000L + 621355968000000000L, TimeSpan.Zero);
        }

        public static long ToUnixTimeSeconds(this DateTimeOffset utcDateTime)
        {
            return utcDateTime.Ticks / 10000000L - 62135596800L;
        }

        public static long ToUnixTimeMilliseconds(this DateTimeOffset utcDateTime)
        {
            return utcDateTime.Ticks / 10000L - 62135596800000L;
        }

        [Test]
        public void UnixSeconds()
        {
            DateTime utcNow = DateTime.UtcNow;
            DateTimeOffset utcNowOffset = new DateTimeOffset(utcNow);

            long unixTimestampInSeconds = utcNowOffset.ToUnixTimeSeconds();

            DateTimeOffset utcNowOffsetTest = UnixDateTime.FromUnixTimeSeconds(unixTimestampInSeconds);

            Assert.AreEqual(utcNowOffset.Year, utcNowOffsetTest.Year);
            Assert.AreEqual(utcNowOffset.Month, utcNowOffsetTest.Month);
            Assert.AreEqual(utcNowOffset.Date, utcNowOffsetTest.Date);
            Assert.AreEqual(utcNowOffset.Hour, utcNowOffsetTest.Hour);
            Assert.AreEqual(utcNowOffset.Minute, utcNowOffsetTest.Minute);
            Assert.AreEqual(utcNowOffset.Second, utcNowOffsetTest.Second);
        }

        [Test]
        public void UnixMilliseconds()
        {
            DateTime utcNow = DateTime.UtcNow;
            DateTimeOffset utcNowOffset = new DateTimeOffset(utcNow);

            long unixTimestampInMilliseconds = utcNowOffset.ToUnixTimeMilliseconds();

            DateTimeOffset utcNowOffsetTest = UnixDateTime.FromUnixTimeMilliseconds(unixTimestampInMilliseconds);

            Assert.AreEqual(utcNowOffset.Year, utcNowOffsetTest.Year);
            Assert.AreEqual(utcNowOffset.Month, utcNowOffsetTest.Month);
            Assert.AreEqual(utcNowOffset.Date, utcNowOffsetTest.Date);
            Assert.AreEqual(utcNowOffset.Hour, utcNowOffsetTest.Hour);
            Assert.AreEqual(utcNowOffset.Minute, utcNowOffsetTest.Minute);
            Assert.AreEqual(utcNowOffset.Second, utcNowOffsetTest.Second);
            Assert.AreEqual(utcNowOffset.Millisecond, utcNowOffsetTest.Millisecond);
        }
    }

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