Time Management answers the following kind of questions:
"WHEN am I busy? WHEN is my next meeting"
Time management is made up of constraints.
Task Management answers another type of questions like:
"WHAT do I have to do? WHAT can I do now?"
Task Management is more about work, being agile and flexible, and tends to fill in the blanks around the time constraints we have.
A lot of people mix their calendar (which is about time management) and their to do list (which is about task management) by adding their tasks in their calendar. Besides the fact that it can get really messy, there is another question to ask: Do all my tasks must have a due date? Well, not necessarily.
Of course some tasks have a due date, but I rather organize them according to the day I want to work on them than according to the day I have to deliver my work. Therefore, due dates should be used only when really needed, but certainly not systematically. Otherwise your work organization becomes inflexible, and you end up managing dates that do not have any sense in most cases, and doing more work about work.
Regarding my personal organization, I manage my time and my tasks separately. Sometimes, when it's needed, I connect one to each other, but I rather keep my personal organization flexible.