This will help you understand how task scheduling takes place in a project. Many a time, the project automatically moves a task to a different time than expected, or changing a value of a task (let’s say task constraint) changes the task scheduling. Let’s understand how project scheduling works and how other factors affect task scheduling.

How is the task schedule affected by Manual and Automatic Scheduling?

When you create a manually scheduled task, its dates are not changed by the scheduler engine and you have to schedule the task as per your needs. This is okay if we have limited and less complicated tasks but when the projects get complicated you might need the scheduling engine to schedule the task for you as per the task dependencies (links), task constraints, and other elements applied to them. So, you might need the automatically scheduled tasks that can be drawn by the scheduler engine and you don’t have to look after them.

No matter whether it’s a manually scheduled task or an automatically scheduled task when you create a new task, the Start Date, Finish Date, and duration of the task are set by default. And according to these values, the bars of the tasks are drawn in the Gantt chart view.

Note: In Advance Scheduling, the duration of the task is calculated and shown in hours.

Since the manually scheduled tasks are scheduled by the user, if you change the start date or finish date of a task, the project recalculates the duration accordingly and plots the same in the Gantt chart view.

Manually Scheduled Task

The manually scheduled tasks can be placed anywhere in the schedule and are not moved by the project. This provides you the control and flexibility of how you want to plan and manage your schedule.

Manually scheduled tasks are useful in scenarios where project managers do not have complete information about the projects, for example, they might know the start date of the project but the end date or the number of resources for the project is unknown. In such cases, they might want to drive the project as and when they receive the remaining information such as the count of resources, percentage allocation of the resources, or an estimate of the total work required to finish the tasks.

Important Points:

  • You can change a task from automatically scheduled to manually scheduled and vice versa. However, you need to be careful while doing that as the project makes changes to the task schedule accordingly.
  • In manually scheduled tasks, the task types are respected by the project while the dependencies and constraints are not respected.

The following table shows the project behavior in the case of automatically scheduled tasks and manually scheduled tasks.


Manually Scheduled

Automatically Scheduled

Resources Resources can be assigned to tasks. The project doesn’t use a resource calendar for scheduling. Resources can be assigned to tasks. The project uses the resource calendar for effective scheduling.
Constraints Not considered by the project Considered and used by the project for scheduling.
Dependencies (links)


Can be applied but the scheduling of the task won’t change due to dependency. Although, it reschedules a task when first applied. Is used and changes the scheduling of the task.
 Project and Resource Calendars Not considered by the project. Considered and used by the project for scheduling.

Automatically Scheduled Tasks

The automatic tasks allow you to schedule your tasks in a systematic and structured way. The automatically scheduled tasks are scheduled with the earliest and latest dates as per the inputs given by the user such as task duration, planned work, constraints date, task links (dependencies), and the number of resources.

The project is scheduled based on the given information provided by the user –

  1. The overall project
  2. The individual tasks required to complete the project.
  3.  Resources required to complete the tasks

If you change anything in the project after creating the schedule, you can update the resources or tasks and the schedule is automatically adjusted by the project.

You might provide one or all of the given information –

  1. Constraints
  2. Duration
  3. Tasks dependencies

The project calculates the Start date and the Finish date for each task using this information.

You can add resources and assign them to the task to make them responsible for finishing the given task. This will help you plan for your project as well as to calculate the materials required to finish the task. If you provide resources, the tasks further refine the schedule according to the following information –

  1. Units
  2. Work
  3. Working time (as entered in the calendars)

Note: Other factors such as resource availability, lead time, the lag time for task dependencies, task types, and the number of resources can also affect the scheduling.

Changing the task scheduling modes

You can change a task from automatically scheduled to manually scheduled and vice versa.

Rescheduling of Past Due Tasks

Past due tasks are the ones that are not completed on their planned finish date and have remaining efforts on them even after their planned finish date.
The Past due tasks are not rescheduled automatically whether the task is auto-scheduled or manually scheduled task. If there is any past due task then a message is shown on the checkout indicating the revised potential finish date of the task. For example, if the planned start and planned finish date of a task are 14 July and 15 July respectively and the task is past due on 16 July having remaining efforts as 50%, then the revised potential planned end date of the task will be 17 July and a message will be shown for the same.

How is the Task Schedule affected by the Calendar?

The calendar affects the task schedule as it determines the standard working time for resources. It helps determine the non-working days such as holidays and weekends.

Note: Any changes to the project or resource calendar will not change the dates on the manually scheduled task.

The project calendar helps determine the availability of resources in the project, how the tasks are scheduled and how the resources (assigned to tasks) are scheduled. Initially, the project calendar is used to schedule a task. If any task has resources assigned to it, then the resource calendar is also used in scheduling.

In other words, task-level duration and date computation is done based on the project calendar and assignment-level computations are done based on the respective resource calendar.



Project Calendar Sets the standard working time for the project as a whole. These are used by the tasks by default. If a resource calendar is not used, tasks are scheduled according to the working time defined in the project calendars.
Resource Calendar


The resource calendar allows you to set/determine the working and non-working times for specific resources. The availability of a resource or a set of resources for work might be different from the standard working time defined in the project calendar. In that case, the tasks are scheduled according to the availability of the resources working time of the resources defined in the resource calendar. This change in the working time may affect the finish date of the task.

How is the Task Schedule affected by Resource Assignments?

By default, the project schedule is calculated according to the task dependencies (links), applied constraints, task duration, and project calendars until a resource is assigned to a task. When you assign a resource to a task, the resource calendar and assignment units also participate in scheduling the task giving more accurate calculations.

Note: Resource calendars do not affect the manually scheduled tasks. The scheduling of a manually scheduled task doesn’t change as per the resource calendar even if you assign a resource to it.

Once you assign resources to a task, the project calculates the schedule using the additional resource and assignment information as shown in the following table –

Resource attribute


Work The total amount of work (including the overtime work if any) the resource is assigned to do. It also includes how the work is distributed over time.
Assignment units The amount of the assignment units for the resource on the task – whether the availability of the resource on the task is full-time ( 100%), part-time (50%), etc.
Task type If you revise the existing type of tasks, the task type affects schedule change.
Calendar The project schedules the assigned resources as per their working and non-working time set in their resource calendars.

Apart from the above points, task constraints and task dependency also affect the scheduling of a task.

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