In this tutorial, you will learn how to get project start date when we have start day and project duration in workdays. This is possible by using Excel WORKDAY function. This function returns a date in a specific range (before or after selected date). In our case, it will return a start date based on end date and project duration in days.
Get project start date
=WORKDAY(end_date, - duration_days, [holidays])
The WORKDAY function returns a date in a specific range, before or after a selected date. The function can take in count specified holidays, but it is not mandatory.
The parameters of the function are: end_date – a finishing date of a project for which we want to get a start date; duration_days – a duration of a project for which we want to get a start date – in our case it will be negative, because we have to subtract it from end date; holidays is a non-obligatory parameter which enables the function to take in counts holiday dates and skip them. To enable this, we need to create a table with all holiday’s dates. Also, we need to define a name for range containing holidays’ dates.
In the following example, we will see how to get project start date, if we have ending date and duration of a project in workdays. We will also take in count holidays while calculating the start date. Let’s see how the formula looks like:
=WORKDAY(C3, -D3, public_holidays)
Figure 1. Get project start date
As you can see in the picture, in column B (“Project”), we have project names. In column C (“End date”), we have end dates of projects, while in column D (“Workdays”) we have a length of every project in working days. In the column E (“Start date”) we want to get a start date of every project.
First of all, we created a new table which has the list of holidays and their dates and named the range G3:G6 “public_holidays”.
In the example, we want to get a project start date based on cells C3 and D3 and put it in the cell E3. Therefore, our end date will be 16-Feb-18 and project duration 15 working days. As 15-Feb-18 is the Holiday, the formula will skip this date and weekends and return 25-Jan-18 in the cell E3 as the start date of the Project 1.