Convert between calendars in Universal Apps

Question

The Universal Windows Platform (UWP) DateTime doesn't seem to support this constructor of DateTime ( link ).

DateTime Constructor (Int32, Int32, Int32, Calendar)

A core functionality of the app I am writing is to convert DateTimes between different Calendar formats (eg gregorian, hijri, hebrew), and previously I relied on that constructor for performing the conversion.

Any idea how I could perform date conversion on a Universal App now that this ctor is missing? eg convert a Hijri/Hebrew Date to Greogiran?

-Tariq

Answer 1

If you want to use .NET classes, these is a ToDateTime method in Calendar class to convert a date in that calendar to a DateTime (Gregorian):

int persianYear = 1394;
int persianMonth = 8;
int persianDay = 10;

var persianCalendar = new System.Globalization.PersianCalendar();
DateTime gregDateTime = persianCalendar.ToDateTime(persianYear, persianMonth, persianDay, 0, 0, 0, 0);
Debug.WriteLine(
   string.Format(
      "{0}/{1}/{2} in persian is {3}/{4}/{5} in gregorian",
      persianYear,
      persianMonth,
      persianDay,
      gregDateTime.Year,
      gregDateTime.Month,
      gregDateTime.Day
   ));

output:

1394/8/10 in persian is 2015/11/1 in gregorian

There are also GetYear , GetMonth and similar methods to convert back.

But if you want to go with Windows Runtime Classes (Recommended), the Calendar class is available with a ChangeCalendarSystem method to do the conversion. You can use Year, Month and Day properties to get and set date components.

Here is a sample convert method that converts date components from a calendar system to another:

private void ConvertDate(
   string from,
   int year,
   int month,
   int day, 
   string to,
   out int convertedYear,
   out int convertedMonth,
   out int convertedDay) {

   Calendar calendar = new Calendar();
   calendar.ChangeCalendarSystem(from);
   calendar.Year = year;
   calendar.Month = month;
   calendar.Day = day;
   calendar.ChangeCalendarSystem(to);
   convertedYear = calendar.Year;
   convertedMonth = calendar.Month;
   convertedDay = calendar.Day;
}

An example to use the method to convert Persian to Hijri and Hijri to Gregorian:

int persianYear = 1394;
int persianMonth = 8;
int persianDay = 10;

int hijriYear;
int hijriMonth;
int hijriDay;

ConvertDate(
   CalendarIdentifiers.Persian,
   persianYear,
   persianMonth,
   persianDay,
   CalendarIdentifiers.Hijri,
   out hijriYear,
   out hijriMonth,
   out hijriDay);

Debug.WriteLine(
   string.Format(
      "{0}/{1}/{2} in Persian is {3}/{4}/{5} in Hijri",
      persianYear,
      persianMonth,
      persianDay,
      hijriYear,
      hijriMonth,
      hijriDay
   ));

int gregYear;
int gregMonth;
int gregDay;

ConvertDate(
   CalendarIdentifiers.Hijri,
   hijriYear,
   hijriMonth,
   hijriDay,
   CalendarIdentifiers.Gregorian,
   out gregYear,
   out gregMonth,
   out gregDay);

Debug.WriteLine(
   string.Format(
      "{0}/{1}/{2} in Hijri is {3}-{4}-{5} in Gregorian",
      hijriYear,
      hijriMonth,
      hijriDay,
      gregYear,
      gregMonth,
      gregDay
   ));

Output:

1394/8/10 in Persian is 1437/1/19 in Hijri

1437/1/19 in Hijri is 2015/11/1 in Gregorian