There is a public Google calendar which has the HALO events. It shows recent and future events and is automatically maintained from the web site events database.
The URLs are:
For Android devices the easiest way is to add the ICS link above as an "Other Calendar" on the web page of your Google Calendar. On your device enable the HALO calendar that should then appear and SYNC. (The ICSDroid chargeable appp may be another way).
For iPhone (IOS6 - IOS10 tested) go to Settings and select Mail,Contacts,Calendars. Select Add account. Select Other (N.B. do not select Google). Select Add Subscribed Calendar. Enter or paste the ICS URL above into the Server field and touch Next. That's pretty much it. You have to go to your calendar, touch calendars and make sure the haloorie one is ticked. You can also set the colour to blue.
For Thunderbird with the Lightning add on select the Calendar pane. Right click near or on the existing calendar(s) and select New calendar. Select On the network and click next. Select iCalendar (ICS) and paste the ICS URL from above into the Location field. Select Offline support to maintain a local copy if you want. Click Next. Enter a meaningful name e.g. HALO events in the Name field and select a colour e.g. light blue. Click Next, then Finish.
For people using other mobile devices or calendar systems, please try it out and report success (or otherwise) to me and I will add it to this page on the web site in due course.