How to Convert DateTime value to OADate format using ToOADate function in UWP platform?

Question

I am using DateTime.FromOADate() and DateTime.ToOADate() function in WPF and WinForms platform for convert the DateTime value to OADate format. But which functions not available in UWP platform. So anyone can suggest your opinion to convert the dateTime value to OADate format in UWP platform.

Answer 1

How to Convert DateTime value to OADate format using ToOADate function in UWP platform?

You could write your own ToOADate method by reference the .Net reference source. For example, the following is a simple demo for ToOADate and FromOADate functions you may test it.

private void btndatetime_Click(object sender, RoutedEventArgs e)
{
    DateTime fromOA = FromOAdate(40967.6424503935);
    System.Diagnostics.Debug.WriteLine(fromOA);
    double toOA = ToOAdate(fromOA);
    System.Diagnostics.Debug.WriteLine(toOA);
}
public DateTime FromOAdate(double oadate)
{
    return new DateTime(DoubleDateToTicks(oadate), DateTimeKind.Unspecified);
} 
public double ToOAdate(DateTime datetime)
{
    return TicksToOADate(datetime.Ticks);
}
private const long TicksPerMillisecond = 10000;
private const long TicksPerSecond = TicksPerMillisecond * 1000;
private const long TicksPerMinute = TicksPerSecond * 60;
private const long TicksPerHour = TicksPerMinute * 60;
private const long TicksPerDay = TicksPerHour * 24;
private const UInt64 TicksMask = 0x3FFFFFFFFFFFFFFF;
private const long DoubleDateOffset = DaysTo1899 * TicksPerDay;
// Number of days in a non-leap year
private const int DaysPerYear = 365;
// Number of days in 4 years
private const int DaysPer4Years = DaysPerYear * 4 + 1;       // 1461
// Number of days in 100 years
private const int DaysPer100Years = DaysPer4Years * 25 - 1;  // 36524
// Number of days in 400 years
private const int DaysPer400Years = DaysPer100Years * 4 + 1; // 146097
private const int DaysTo1899 = DaysPer400Years * 4 + DaysPer100Years * 3 - 367;
// Number of milliseconds per time unit
private const int MillisPerSecond = 1000;
private const int MillisPerMinute = MillisPerSecond * 60;
private const int MillisPerHour = MillisPerMinute * 60;
private const int MillisPerDay = MillisPerHour * 24;
private static double TicksToOADate(long value)
{
    if (value == 0)
        return 0.0;  // Returns OleAut's zero'ed date value.
    if (value < TicksPerDay) // This is a fix for VB. They want the default day to be 1/1/0001 rathar then 12/30/1899.
        value += DoubleDateOffset; // We could have moved this fix down but we would like to keep the bounds check.          
    long millis = (value - DoubleDateOffset) / TicksPerMillisecond;
    if (millis < 0)
    {
        long frac = millis % MillisPerDay;
        if (frac != 0) millis -= (MillisPerDay + frac) * 2;
    }
    return (double)millis / MillisPerDay;
}
internal static long DoubleDateToTicks(double value)
{
    // The check done this way will take care of NaN
    //if (!(value < OADateMaxAsDouble) || !(value > OADateMinAsDouble))
    //    throw new ArgumentException(Environment.GetResourceString("Arg_OleAutDateInvalid"));
    // Conversion to long will not cause an overflow here, as at this point the "value" is in between OADateMinAsDouble and OADateMaxAsDouble
    long millis = (long)(value * MillisPerDay + (value >= 0 ? 0.5 : -0.5));
    // The interesting thing here is when you have a value like 12.5 it all positive 12 days and 12 hours from 01/01/1899
    // However if you a value of -12.25 it is minus 12 days but still positive 6 hours, almost as though you meant -11.75 all negative
    // This line below fixes up the millis in the negative case
    if (millis < 0)
    {
        millis -= (millis % MillisPerDay) * 2;
    }

    millis += DoubleDateOffset / TicksPerMillisecond;
    //if (millis < 0 || millis >= MaxMillis) throw new ArgumentException(Environment.GetResourceString("Arg_OleAutDateScale"));
    return millis * TicksPerMillisecond;
}