As a professional marketer, timelines and deliverables are non-negotiable. Deadlines are usually firm.
For most of my projects, I provide a Gantt Chart to my clients to see the project timeline. The Gantt includes defining the weeks when I need client approval, so we can assure the right people will be available.
A Gantt Chart is a bar chart with project milestones in the first column. Each column represents a period of time, usually a week. Here is an example of a basic Gantt Chart:
I create most of my Gantt Charts in a simple Excel spreadsheet. Once I have create a spreadsheet for the new year, I simply replicate it as necessary for each new project.
There are also free templates online.
However, more complex projects may require Gantt software. There are many options from which to choose. I like SmartSheet; it is easy-to-use and affordable. As with most platforms, SmartSheet offers a 30-day free trial.
Some of my associates use Sciforma or Mavenlink (more advanced project management software). I have not used them personally, so I can't share more on those.
Whatever tool you use to manage your timelines, you will never go wrong by delivering on, or before, your deadline.