Pronto webmail - sharing calendars
You can share your calendars or access other people's from the Calendar view of the Pronto webmail.
If you want to access a previously shared calendar, click on the plus sign on the bottom-left corner, and choose "Calendar subscription": in the little pane that will appear, type the id number or the name of the person who shared his/her calendar with you (hint: type a few characters and wait for autocompletion), then click on the checkboxes near the calendars that you want to access: they will appear on the left section of the Calendar view, under the name of the sharer.
If you want to share one of your calendars, right click on it and choose "Lista controllo accessi" ("Access control list"): in the little pane that will appear, type "d" + the id number of the person to whom you want to grant access (e.g., if you want to grant access to 013185, you would type d013185), then choose the proper permissions ("Read", "Write", "Admin", or "Custom"), and click on Save. An email will automatically be sent to that person, allowing him/her to subscribe to the calendar directly from the mail message clicking on the "Subscribe" button (available only in Pronto), or by following the procedure described in the previous paragraph.