There is a database of past and future Devon Junior events on the Devon Junior Chess Association website.
Tim Onions also keeps a list of junior events on his website:
The list of Devon junior events is mirrored on an open Google Calendar:
[Try the Agenda view]
Similar Google Calendar lists are maintained by me for:
Exeter Chess Club events:
Devon County Chess Association and other SW chess events:
You should be able to view and use Google calendars on your smartphone.
The Junior and Devon calendars are shown together on a web page here:
The Exeter, Devon and Junior calendars are shownin a little box on the Exeter front page, with links to Google:
Lastly, there is a nicely-organised list of all chess events kept by the English Chess Federation:
Please let me know if I have missed anything - an event from a calendar, or a calendar from this list!