If your task is "deliver software with these 10 features until 15 August" then you've got to know if you're on track or not. - You've got to know what the task

If your task is "deliver software with these 10 features until 15 August" then you've got to know if you're on track or not. - You've got to know what the tasks are that still need to be done, and their current estimates. - Given the people on your team, how long they work per week, what public holidays there are, when they are going on vacation, you can work out how much work capacity is available to you until the deadline. How do these compare? As the project progresses, no doubt slips will occur, requirements might change etc. Continuing to model the set of tasks ahead of you allows you to understand if the current plan will make you meet your target or not. If you already know, two months ahead of the deadline, "we're not going to make it", you can do something about it. Inform the customer. Hire more people. Reduce the requirements. Schedule overtime. Etc. If you don't know, then you're just driving blind. The 14th August will roll around, and you'll notice "oh, the project's not done, and now it's too late to do anything about it". This is where tools can help you. Model all the tasks. Model all the expected durations (range estimates ideally to model uncertainty like LiquidPlanner or FogBugz does). Model when people are on holiday, how long they work per week. Know as soon as possible when things are no longer on track, so you can take action.