Task’s schedule is designed to be flexible. Other than a specific date, you can set the due day to “Until done” or a day range (3 days, a week, a month,...). If the due date is over then the task will be listed as “Overdue” on My Day tab.
For tasks that you plan to do but haven’t decided when yet then you can put them in Backlog.
You can set multiple reminders for a task or even reminders for each subtask.
A task can have multiple instances, each with a different due time. You can config the task to repeat automatically (daily, monthly,...) or you can manually assign the dates that it will occur.