# Simple duration vs relative duration

How much work is required to complete a task can be expressed as a "relative duration".

Relative duration determines the expected due date and time relative to the starting time. Examples of relative durations include "Next business day by 4pm", or "2 business days by 10:30am".

To calculate a relative duration, the calendar and time zone must be considered to determine what "next business day" means since it is the calendar that defines which days are valid work days and the time zone will affect the result as well. As an example, consider "Next business day by 4pm":
• If it is Monday at 12pm: Next business day by 4pm => Tuesday at 4pm
• If it is Friday at 2pm: Next business day by 4pm => the following Monday at 4pm
Note: Next business day is often defined by a starting day and time. For example, "next business day at 4pm if before 2pm" indicates that if the current time is after 2pm on a business day, then "Next business day" really means 2 business days since today does not count.