Author: Oscar Cronquist Article last updated on August 24, 2020


This article demonstrates a formula that points out row numbers of records that overlap the current record based on a start and end date.

cwrbelis asks:
Hi Oscar,Great website! Keep up the good work.I have a question as to how to expand this to the next step. Per your initial example we can see that Jeff in Row 1 and Shaun in Row 4 overlap their work schedule. I would like to know if there were a way, say for instance in Range E6:E12, to display Jeff’s Row number next to Shaun’s name and visa – versa. I can see how this will easily display what record numbers overlap when there is only one overlap in the range. Can we differentiate the records when there are two overlaps? Let’s say Theodor in Row 6 also has an overlap with Thomas in Row 2.Now the data becomes confusing because we have to determine, from the 4 grayed rows, who overlaps with whom.Can a formula return the Row value of the “matching” overlap record?
In Jeff’s E6 cell it would indicate “Row 4” as to the matching record, and the reverse for Shaun. Shaun’s E9 cell would indicate “Row 1” as the matching record.
And at the same time Theodor’s E11 cell would reflect “Row 2” for Thomas’s record and Thomas’ E7 cell would show “Row 6” for Theodor.I haven’t even touched on the tougher one, such as what happens when John in Row 7 has an end date of 2010-01-07, thus overlapping with both Jeff and Shaun!One step at a time. :)Thanks

The array formula in cell F6 returns the rows of overlapping date ranges for the current record. The record on row 6 overlaps with both records on rows 9 and 12.

Records on row 9 and 12 show they overlap with the record on row 6, this makes it much easier to spot overlapping records.

Formula in cell F6:

=IFERROR(SMALL(IF(($C6<=$D$6:$D$12)*($D6>=$C$6:$C$12), IF(ROW($C$6:$C$12)=ROW(), "", ROW($C$6:$C$12)), ""), COLUMNS($A$1:A1)), "")

How to enter an array formula

Identify rows of overlapping records

You need to enter the formula in cell F6 as an array formula if you have an older Excel version than Excel 365 subscription.

  1. Copy above array formula (Ctrl + c).
  2. Double click on cell F6.
  3. Paste above array formula (Ctrl + v).
  4. Press and hold CTRL + SHIFT simultaneously.
  5. Press Enter once.
  6. Release all keys on keyboard.

The formula now has a beginning and ending curly bracket, like this: {=array_formula}

How to copy array formula

Identify rows of overlapping records copy formula

  1. Select cell F6.
  2. Click and hold left mouse button on the green dot located at the bottom right corner of the selected cell.
  3. Drag with the mouse as far as needed to the right.
  4. Click and hold left mouse button on the green dot located at the bottom right corner of the selected cell range.
  5. Drag with the mouse downwards as far as needed.

The formula contains relative cell references, they change when the cell is copied. You need to copy cells to get this to work.

Concatenated row numbers

Identify rows of overlapping records row numbers concatenated

If you rather have row numbers concatenated in a single cell use the following formula.

=TEXTJOIN(", ", TRUE, IF(($C6<=$D$6:$D$12)*($D6>=$C$6:$C$12), IF(ROW($C$6:$C$12)=ROW(), "", ROW($C$6:$C$12)), ""))

The TEXTJOIN function is available for Excel 365 subscribers, there is also User Defined Function (UDF) on the same webpage if you own an earlier version of Excel.

Explaining formula in cell F6

Identify rows of overlapping records examine formula

I recommend using the "Evaluate Formula" tool located on the Formula tab on the ribbon. Click the "Evaluate Formula" button, a dialog box appears, see image above.

Click the Evaluate button to see next calculation step.

Step 1 - Identify overlapping date ranges

The logical operators <> and = allow you to compare dates and find overlapping date ranges.

($B6<=$C$6:$C$12)*($C6>=$B$6:$B$12)

becomes

({TRUE; TRUE; TRUE; TRUE; TRUE; TRUE; TRUE})*({TRUE; FALSE; FALSE; TRUE; FALSE; FALSE; TRUE})

becomes

{1;0;0;1;0;0;1}

Identify rows of overlapping records logical expressions 1

If you multiply boolean values you get this in Excel:

  • TRUE * TRUE = 1
  • TRUE * FALSE = 0
  • FALSE *FALSE = 0

This is AND logic and the asterisk allows you to multiply arrays row-wise.

Identify rows of overlapping records array 1

If you use the AND function it will apply AND logic to all values and return a single value, that is the reason we can't use it here.

We want it to return an array so we can easily identify the overlapping date ranges.

The array has the same number of values as there are date ranges, the position in the array corresponds to the position in the list of records.

Step 2 - Create an array containing row numbers except for the current row number

To be able to return the correct row numbers we must create an array that is equally large as the previous array.

We don't want to return the date range for the current record so we need to figure out a way to remove the current row number from the array.

IF(ROW($C$6:$C$12)=ROW(), "", ROW($C$6:$C$12)), "")

becomes

IF({6;7;8;9;10;11;12}=6, "", {6;7;8;9;10;11;12}, "")

returns

{"";7;8;9;10;11;12}

Identify rows of overlapping records array1

Step 3 - If current date range overlaps another date range then return row number

The logical expressions we built in step 1 is now used in an IF function to extract the correct row numbers of date ranges that overlap.

IF(($B6<=$C$6:$C$12)*($C6>=$B$6:$B$12), IF(ROW($B$6:$B$12)=ROW(), "", ROW($B$6:$B$12)), "")

becomes

IF({1;0;0;1;0;0;1}, {"";7;8;9;10;11;12}, "")

returns

{"";"";"";9;"";"";12}

Identify rows of overlapping records array2

Step 4 - Find the k-th smallest row number

The last step is to extract the smallest number based on where in worksheet the formula is calculated.

SMALL(IF(($B6<=$C$6:$C$12)*($C6>=$B$6:$B$12), IF(ROW($B$6:$B$12)=ROW(), "", ROW($B$6:$B$12)), ""),COLUMN(A1))

becomes

SMALL({"";"";"";9;"";"";12}, COLUMN(A1))

The COLUMN function calculates the column number based on a cell reference. The cell reference A1 is relative meaning it changes when the cell is copied to cells to the right.

SMALL({"";"";"";9;"";"";12}, COLUMN(A1))

becomes

SMALL({"";"";"";9;"";"";12}, 1)

and returns 9 in cell F6.

In cell G6 the formula changes to

SMALL({"";"";"";9;"";"";12}, COLUMN(B1))

and becomes

SMALL({"";"";"";9;"";"";12}, 2)

and returns 12 in cell G6.

Download Excel file


Identify-overlapping-date-rangesv3.xlsx

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