How to create a formula for days elapsed in a quarter

How to create a Row-Level Formula for Days Elapsed in a Quarter:

Use a Row-Level Formula to display the Number of Days Elapsed in a Quarter on a Report.

Here are the instructions for creating a row-level formula to calculate the number of days between the start of the quarter and the close date within the same quarter.

Step1. Login to your Salesforce account
Step 2. In the navigation bar at the top, click on the App Launcher  and search for Reports. Click on the Reports 
Step 3. From the Reports tab, click New Report
Step 4. Select the Opportunities report type for the report, and click Start Report
Step 5. Save the report with a name of your choosing 
Step 6. From the Columns section of the Outline pane, click  | Add Row-Level Formula
 

Step 7. From the Edit Row-Level Formula Column window, enter a Column Name (2), choose a Formula Output Type of Number (3), set the number of Decimal Points to 0 (4), and use the Formula below (See Sample Formulas) (5). To test your formula for errors, click Validate. If necessary, resolve any errors. Then, click Apply (6).
 

Sample Formulas: 

CLOSE_DATE -
IF(
MONTH(CLOSE_DATE) < 4,
DATE( YEAR(CLOSE_DATE), 01, 01),
IF(
MONTH(CLOSE_DATE) < 7,
DATE( YEAR(CLOSE_DATE), 04, 01),
IF(
MONTH(CLOSE_DATE) < 10,
DATE( YEAR(CLOSE_DATE), 07, 01),
DATE( YEAR(CLOSE_DATE), 10, 01)
)))

Note: This version does not include the first IF statement like the formulas below because there is no need to check if the month is less than 1, as it would always evaluate to false. 

CLOSE_DATE -
IF(
MONTH(CLOSE_DATE) < 2,
DATE( YEAR(CLOSE_DATE) - 1, 11, 01),
IF(
MONTH(CLOSE_DATE) < 5,
DATE( YEAR(CLOSE_DATE), 02, 01),
IF(
MONTH(CLOSE_DATE) < 8,
DATE( YEAR(CLOSE_DATE), 05, 01),
IF(
MONTH(CLOSE_DATE) < 11,
DATE( YEAR(CLOSE_DATE), 08, 01),
DATE( YEAR(CLOSE_DATE), 11, 01)
))))

CLOSE_DATE - 
IF( 
MONTH(CLOSE_DATE) < 3,
DATE( YEAR(CLOSE_DATE) - 1, 12, 01),
IF( 
MONTH(CLOSE_DATE) < 6,
DATE( YEAR(CLOSE_DATE), 03, 01),
IF( 
MONTH(CLOSE_DATE) < 9,
DATE( YEAR(CLOSE_DATE), 06, 01),
IF( 
MONTH(CLOSE_DATE) < 12,
DATE( YEAR(CLOSE_DATE), 09, 01),
DATE( YEAR(CLOSE_DATE), 12, 01)
))))

Step 8. To save and run the report, click Save & Run

You're Done!