Time Reserve is a scheduled time period that protects a task from delays, breaks or other factors that may extend the task’s duration. It creates schedule buffers that prevent undesired variations and help reach task completion by the target date.
Using time reserves is great in ensuring accuracy and safety of task scheduling because a reserve pool of time helps avoid time variations and predict undesired issues. For example, Reserve Analysis uses time reserves as the major tool in estimating task duration. This method determines an amount of time that is necessary to offset undesired issues (e.g. lack of funds, technical failure) which may affect task completion date.
Time reserves are like "buffers" that protect from time-related issues. Buffers are added to task schedules to avoid performance gaps and hence ensure task success. They help analyze current progress of tasks and understand what corrective actions need to be taken to settle issues. In this context, time reserves in Reserve Analysis are close to project buffers in CCPM (Critical Chain Project Methodology).