C# - Convert DateTime to Long and Vice Versa

Transform datetime to long or long to datetime in C#.

Follow @AbhithRajanAbhith RajanOctober 29, 2019 · 2 min read · Last Updated: October 29, 2019

Story behind this post is when I started working with an existing MSSQL DB, I had to convert the DateTime to long since action auditing fields such as CreationTime, LastUpdated etc was stored as numeric.

eg, 20191028091320.

First of all, I don’t like storing DateTime in numeric format like above, which brings so much overhead during dealing with the same field, like querying based on date, formatting for displaying etc.

The way I handled these conversions given below,

DateTime to Long

1long.Parse(DateTime.UtcNow.ToString("yyyyMMddHHmmss"))

Long to DateTime

The below code can handle 14 digits (eg. 20191028091320), 16 digits (eg. 2019102809132000 ) and 8 digits (eg. 20191028).

1private static DateTime? GetDateTimeFromInt(long? dateAsLong, bool hasTime = true)
2{
3    if (dateAsLong.HasValue && dateAsLong > 0)
4    {
5        if (hasTime)
6        {
7            // sometimes input is 14 digit and sometimes 16
8            var numberOfDigits = (int)Math.Floor(Math.Log10(dateAsLong.Value) + 1);
9
10            if (numberOfDigits > 14)
11            {
12                dateAsLong /= (int)Math.Pow(10, (numberOfDigits - 14));
13            }
14        }
15
16        if (DateTime.TryParseExact(dateAsLong.ToString(), hasTime ? "yyyyMMddHHmmss" : "yyyyMMdd",
17                                  CultureInfo.InvariantCulture,
18                                  DateTimeStyles.None, out DateTime dt))
19        {
20            return dt;
21        }
22    }
23
24    return null;
25}

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C# - Convert DateTime to Long and Vice Versa

Transform datetime to long or long to datetime in C#.

DateTime to Long

Long to DateTime

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