Data Type Date (date field: A type of field whose content is a date. Examples include the Baseline Start and Early Finish fields.)
Entry Type Calculated (calculated field: A field in which the value is determined by Project based on information in other fields. Project may recalculate the value automatically or when you specify, depending on your choice of calculation settings.)
Description The Late Start field contains the latest date that a task can start without delaying the finish of the project. This date is based on the task's start date, as well as on the late start and late finish dates of predecessor (predecessor: A task that must start or finish before another task can start or finish.) and successor (successor: A task that cannot start or finish until another task starts or finishes.) tasks, and other constraints (constraint: A restriction set on the start or finish date of a task. You can specify that a task must start on or finish no later than a particular date. Constraints can be flexible [not tied to a specific date] or inflexible [tied to a specific date].).
How Calculated When you first create a task, its late start date is the same as the project finish date minus the task duration (duration: The total span of active working time that is required to complete a task. This is generally the amount of working time from the start to finish of a task, as defined by the project and resource calendar.). As you link the task to predecessors and successors and apply any other constraints, Microsoft Office Project calculates the late start date as the last possible date this task could be started if all predecessor and successor tasks also start and finish on their late start and late finish dates. These calculations are based on a fixed task duration. If there is a leveling delay on successor tasks, this delay is also figured into the date in the Late Start field.
Best Uses Add the Late Start field to a task view, along with the Early Start, Early Finish, and Late Finish fields, to analyze slack (slack: The amount of time that a task can slip before it affects another task or the project's finish date. Free slack is how much a task can slip before it delays another task. Total slack is how much a task can slip before it delays the project.) time in your schedule.
Example Several critical tasks are slipping and are likely to cause the entire project to be severely delayed. You add the Early Start, Early Finish, Late Start, and Late Finish fields to the Task Sheet view, so that you can analyze the delays and find any available slack time.