I apologize if I am just missing this, but is there an option to be notified whenever I enter a task whose date and time would conflict or overlap with another scheduled task?
Unfortunately, that's not possible right now, but you can hover over the date in the mini calendar and you will see if there are tasks scheduled for this day at the bottom of the mini calendar.
Alternatively, you can simply type the day or date in the search box in the top-left corner (type: "Fri" or "30/4", for example) and see tasks across all projects scheduled for this day. Also, when you use the "Quick Add" feature and set a due date for a task, when you save it, you will be redirected to the date view seeing what other tasks are scheduled for this day.
Thank you so much, David. Do you know if this is something that is in the works?
Unfortunately, that's not something we're working on right now, but we will surely consider it in the future and you're welcome to add a request for it to our Votebox: http://todoist.com/Vote/
Thank you, David. Added to the Votebox!