Hi Susan,

The Gantt chart timescale can display the day numbers instead of the date. Right click on the Gantt chart timescale and choose "Timescale" from the shortcut menu. Select the Bottom tier and select the appropriate label from the list.

You may also calculate the number of days from the Project Start to the start of any other task.

Add a text field (for example Text1) to the table.
Right click on the field header and choose "Custom Fields" from the shortcut menu.
Select "Formula" button in the custom attributes section to open the formula dialog.
Enter the following formula:
"Day" & " " & DateDiff("d",[Project Start],[Start])

This will produce an entry "Day 0" for the first task where the start date equals the Project start date. If you want to start with "day 1" as the start date of the first task enter a slightly modified formula:

"Day" & " " & DateDiff("d",[Project Start],[Start])+1