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C# FromOADate and Excel DatesUse the DateTime.FromOADate method, converting numbers like 39456 to a date.
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FromOADate. Excel interop dates are stored as integers. It is possible to convert them to DateTimes. We use FromOADate to convert OLE Automation Dates to real DateTime values. We examine the FromOADate method.

First, you can use FromOADate as a static method on the DateTime type. This method receives one double value as its parameter, and the returns a full DateTime. This will convert those five-digit integers to the regular DateTimes.

DateTime

Array We see an array of OADates you might encounter. Typically the doubles will be somewhere in the 30,000s, but you may encounter outliers.

Array

Next It loops with foreach through each example string. We use a foreach loop to look at each number in the array.

Foreach

Info These numbers would be typically be extracted from Microsoft Excel Interop or some databases.

Excel

FromOADate We show some example calls and output. With Console.WriteLine, we print the results.

Console

C# program that uses FromOADate
using System; class Program { static void Main() { var arr = new string[] { // OA Dates in early 2008. "39456", // (1/9/2008) "39482", "39484", "39493", "39496", "39497", "39501", "39506", "39510", "39513", "39515", "39521", // (3/14/2008) // Different series starts here. "36526", // (1/1/2000) "36557", // (2/1/2000) "39270" // (7//7/2007) }; foreach (string b in arr) { // We must have a double to convert the OA date to a real date. double d = double.Parse(b); // Get the converted date from the OLE automation date. DateTime conv = DateTime.FromOADate(d); // Write to console. Console.WriteLine("{0} = {1}", b, conv.ToShortDateString()); } } }
39456 = 1/9/2008 39482 = 2/4/2008 39484 = 2/6/2008 39493 = 2/15/2008 39496 = 2/18/2008 39497 = 2/19/2008 39501 = 2/23/2008 39506 = 2/28/2008 39510 = 3/3/2008 39513 = 3/6/2008 39515 = 3/8/2008 39521 = 3/14/2008 36526 = 1/1/2000 36557 = 2/1/2000 39270 = 7/7/2007

Values must be double types. The FromOADate method requires that it receive a double value. For the custom code above, we convert the string to a double. You may not need to do this.

Double

Finally We use the static DateTime.FromOADate to turn the double into a regular DateTime.

Static

Input OLE date:
39456 39482 39484 36526 36557 39270

Output DateTime:
1/9/2008 2/4/2008 2/6/2008 1/1/2000 2/1/2000 7/7/2007

Summary. We used the FromOADate method on the DateTime type in the C# language. We saw the input and output. This is a tricky topic and this article serves as an adjunct to my other Excel Interop article.

Note These methods are mainly required for legacy XLS files, which may be replaced with more robust XLSX XML files.

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