GregorianCalendar not found in System.Globalization

Hi,

i have this code in Windows Phone

using System.Globalization;

private static GregorianCalendar gc = new GregorianCalendar();
private HebrewCalendar hc = new HebrewCalendar();

I want to upgrade the project to Universal App.

So, I made a Portable Class Library.

but unfortunately, the System.Globalisation does not include these classes.  (I check with the object browser, and this is not there too).

In msdn, the reference seems to be for Windows 8.1, Windows Phone 8.1 and portable class library.

here's the link:

http://msdn.microsoft.com/en-us/library/system.globalization.gregoriancalendar(v=vs.110).aspx

Why I can find it in .Net for windows phone and not in the regular .Net?