These are mockups and I don’t know if they will be included in Gnome 360.
Arash Mousavi that design the Widget together with William McCann says ” It has to show 2 calendar at same time & their dates. user must be able to select his/her primary & secondary calendar then the main calendar will be primary one & equal days of secondary calendar will be shown next to dates of main calendar.”
For now fellows Persians can use the Persian Calendar Extension by omid.
1- Persian calendar date.
2- Full calendar with support of navigation.
3- It can show, today is holiday or not!
4- Show notification onDayChanged!
5-1- Official solar events.
5-2- Official lunar events.
5-3- Official international events.
5-4- Traditional Persian events.
5-5- Persian personages.
Update 27/06: These designs have been rejected from Gnome Team, but work for a non-Gregorian calendars continues.