Views math expression or Computed field to find date difference in views I have two content type, Bill (Type1) and Cash Receipts (Type2), Type2 referencing Type1 when cash is received.  

In Type1 I have date field called (Bill Issue date), and Type2 I have date field cash receipt date.

So I want to calculate, different between those two dates. I was trying by creating views with two date (by entity reference relationship), then subtract two filed with math expression field, but it return zero.

Actually, I have no idea whether I was wrong or Its not possible to calculate different between dates with views math expression field?

I think, it can be done with Computed Field, I did one within same content type, but I don’t know how to access a field from different content type, please help.

Code that I was used to calculate date for same content type, but how I can access a field from other content type?

If the Machine name of your date-field is 'field_example_date', then the Computed Code (PHP) would be

$startdate = $entity-&gt;field_example_date['und'][0]['value']; // Value of start-date
$enddate = $entity-&gt;field_example_date['und'][0]['value2']; // Value of end-date

$datediff = strtotime($enddate) - strtotime($startdate);
/* The PHP Function STRTOTIME parses the english textual datetime description
 * into a Unix timestamp
 */

$num_leaves = $datediff/(60*60*24);
/* Since we need the number of days IN-BETWEEN, 
 * we divide the resultant difference by 60*60*24 . 
 *
 * Incase of counting no.of days "FROM" to "TO" days, add 1 to the above result.
 * $num_leaves = $datediff/(60*60*24) + 1;
 */

 $entity_field[0]['value'] = $num_leaves;





The Display Code (PHP) will have

$display_output = $entity_field_item['value'];
You can achieve this use a template file, since you can use PHP inside templates in Drupal 7

In your view



Now, add both of your date fields and do this to each of them



In your web directory, go to /sites/all/themes/[yourtheme]/templates folder

Create a file named views-view-fields--[view-name]--[machine-name].tpl.php

EX: views-view-fields--hello-world--block-1.tpl.php

Inside the template file put:

&lt;?php

$date1 = new DateTime('$fields["field_invoice_issue_date"]-&gt;content');
$date2 = new DateTime('$fields["field_payment_receipt_date"]-&gt;content');
$interval = $date1-&gt;diff($date2);
echo "difference " . $interval-&gt;y . " years, " . $interval-&gt;m." months, ".$interval-&gt;d." days "; 

// shows the total amount of days (not divided into years, months and days like above)
echo "difference " . $interval-&gt;days . " days ";

?&gt;


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