sometimes todoist jumps to the year 2014. When I set "6 May" in Jumpbox, todoist shows 6 May of 2014.
because May 6 2013 is already over!?
As Andy mentioned - that's because if you don't include a year, Todoist assumes you want the task to be set to the next occurrence of this date. If you want to schedule a task for the past, please type "6 May 2013" within the due date field.