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Calculate Number of Days Between Two Dates

Calculate the number of days between two given date fields and populate this number into a field on the form.

Last updated | Written by 375 Comments

  • February 10, 2015: Fixed issue where non-US date formats were not working as expected. Added link on demo to alternate version.

  • September 17, 2014: Fixed issue with newer versions of jQuery UI Datepicker where "change" event was not fired when a date was selected and day count was not calculated.

  • March 15, 2013: Updated to fix issue when conditional logic was used on the form.

  • March 3, 2013: Updated to fix issue where "include_end_date" option was not working and added better support for different date formats.

  • March 2, 2013: Updated to support applying to multiple sets of date fields on the same form. Also updated to fix issue where functionality did not run when form was returned due to validation error.

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<?php
/**
* Gravity Wiz // Calculate Number of Days Between Two Gravity Form Date Fields
*
* Allows you to calculated the number of days between two Gravity Form date fields and populate that number into a
* field on your Gravity Form.
*
* @version 1.1
* @author David Smith <david@gravitywiz.com>
* @license GPL-2.0+
* @link https://gravitywiz.com/calculate-number-of-days-between-two-dates/
* @copyright 2013 Gravity Wiz
*/
class GWDayCount {
private static $script_output;
function __construct( $args ) {
extract( wp_parse_args( $args, array(
'form_id' => false,
'start_field_id' => false,
'end_field_id' => false,
'count_field_id' => false,
'include_end_date' => true,
) ) );
$this->form_id = $form_id;
$this->start_field_id = $start_field_id;
$this->end_field_id = $end_field_id;
$this->count_field_id = $count_field_id;
$this->count_adjust = $include_end_date ? 1 : 0;
add_filter( "gform_pre_render_{$form_id}", array( &$this, 'load_form_script') );
add_action( "gform_pre_submission_{$form_id}", array( &$this, 'override_submitted_value') );
}
function load_form_script( $form ) {
// workaround to make this work for < 1.7
$this->form = $form;
add_filter( 'gform_init_scripts_footer', array( &$this, 'add_init_script' ) );
if( self::$script_output )
return $form;
?>
<script type="text/javascript">
(function($){
window.gwdc = function( options ) {
this.options = options;
this.startDateInput = $( '#input_' + this.options.formId + '_' + this.options.startFieldId );
this.endDateInput = $( '#input_' + this.options.formId + '_' + this.options.endFieldId );
this.countInput = $( '#input_' + this.options.formId + '_' + this.options.countFieldId );
this.init = function() {
var gwdc = this;
// add data for "format" for parsing date
gwdc.startDateInput.data( 'format', this.options.startDateFormat );
gwdc.endDateInput.data( 'format', this.options.endDateFormat );
gwdc.populateDayCount();
gwdc.startDateInput.change( function() {
gwdc.populateDayCount();
} );
gwdc.endDateInput.change( function() {
gwdc.populateDayCount();
} );
$( '#ui-datepicker-div' ).hide();
}
this.getDayCount = function() {
var startDate = this.parseDate( this.startDateInput.val(), this.startDateInput.data('format') )
var endDate = this.parseDate( this.endDateInput.val(), this.endDateInput.data('format') );
var dayCount = 0;
if( !this.isValidDate( startDate ) || !this.isValidDate( endDate ) )
return '';
if( startDate > endDate ) {
return 0;
} else {
var diff = endDate - startDate;
dayCount = diff / ( 60 * 60 * 24 * 1000 ); // secs * mins * hours * milliseconds
dayCount = Math.round( dayCount ) + this.options.countAdjust;
return dayCount;
}
}
this.parseDate = function( value, format ) {
if( !value )
return false;
format = format.split('_');
var dateFormat = format[0];
var separators = { slash: '/', dash: '-', dot: '.' };
var separator = format.length > 1 ? separators[format[1]] : separators.slash;
var dateArr = value.split(separator);
switch( dateFormat ) {
case 'mdy':
return new Date( dateArr[2], dateArr[0] - 1, dateArr[1] );
case 'dmy':
return new Date( dateArr[2], dateArr[1] - 1, dateArr[0] );
case 'ymd':
return new Date( dateArr[0], dateArr[1] - 1, dateArr[2] );
}
return false;
}
this.populateDayCount = function() {
this.countInput.val( this.getDayCount() ).change();
}
this.isValidDate = function( date ) {
return !isNaN( Date.parse( date ) );
}
this.init();
}
})(jQuery);
</script>
<?php
self::$script_output = true;
return $form;
}
function add_init_script( $return ) {
$start_field_format = false;
$end_field_format = false;
foreach( $this->form['fields'] as &$field ) {
if( $field['id'] == $this->start_field_id )
$start_field_format = $field['dateFormat'] ? $field['dateFormat'] : 'mdy';
if( $field['id'] == $this->end_field_id )
$end_field_format = $field['dateFormat'] ? $field['dateFormat'] : 'mdy';
}
$script = "new gwdc({
formId: {$this->form['id']},
startFieldId: {$this->start_field_id},
startDateFormat: '$start_field_format',
endFieldId: {$this->end_field_id},
endDateFormat: '$end_field_format',
countFieldId: {$this->count_field_id},
countAdjust: {$this->count_adjust}
});";
$slug = implode( '_', array( 'gw_display_count', $this->start_field_id, $this->end_field_id, $this->count_field_id ) );
GFFormDisplay::add_init_script( $this->form['id'], $slug, GFFormDisplay::ON_PAGE_RENDER, $script );
// remove filter so init script is not output on subsequent forms
remove_filter( 'gform_init_scripts_footer', array( &$this, 'add_init_script' ) );
return $return;
}
function override_submitted_value( $form ) {
$start_date = false;
$end_date = false;
foreach( $form['fields'] as &$field ) {
if( $field['id'] == $this->start_field_id )
$start_date = self::parse_field_date( $field );
if( $field['id'] == $this->end_field_id )
$end_date = self::parse_field_date( $field );
}
if( $start_date > $end_date ) {
$day_count = 0;
} else {
$diff = $end_date - $start_date;
$day_count = $diff / ( 60 * 60 * 24 ); // secs * mins * hours
$day_count = round( $day_count ) + $this->count_adjust;
}
$_POST["input_{$this->count_field_id}"] = $day_count;
}
static function parse_field_date( $field ) {
$date_value = rgpost("input_{$field['id']}");
$date_format = empty( $field['dateFormat'] ) ? 'mdy' : esc_attr( $field['dateFormat'] );
$date_info = GFCommon::parse_date( $date_value, $date_format );
if( empty( $date_info ) )
return false;
return strtotime( "{$date_info['year']}-{$date_info['month']}-{$date_info['day']}" );
}
}
# Configuration
new GWDayCount( array(
'form_id' => 16,
'start_field_id' => 1,
'end_field_id' => 2,
'count_field_id' => 4
) );
view raw gw-gravity-forms-day-count.php hosted with ❤ by GitHub

Have you ever needed to calculate the number of days between two given date fields? Here’s a scenario for consideration.

Let’s say you have a Gravity Form set up to register users for a multi-day event. The user is able to select a start date and end date that they will be attending the event. For each day of attendance they must pay an attendance fee of $10. How can we calculate the total price they should pay for registration?

This snippet will allow to calculate the number of days between two date fields and then populate the calculated number of days into another field. This is beneficial because with this calculated number of days now available as a field value, we can use Gravity Forms’ Calculation Product to correctly calculate the registration fee based on the selected dates.

How do I install this snippet?

Easy peasy. Just copy and paste the code above into your theme's functions.php file.

How do I use this functionality?

To use this snippet’s functionality just go directly below the snippet and instantiate the GWDayCount() class. Instantiate is a big word but all it means is that you’ll be creating a new “instance” of the GWDayCount() class with a set of parameters (aka options) for that specific instance.

Standard Usage

new GWDayCount( array(
'form_id' => 9,
'start_field_id' => 1,
'end_field_id' => 2,
'count_field_id' => 3
) );

Count “Nights” Only
End date is not included in the day count so you are essentially counting the number of “nights” between the two dates.

new GWDayCount( array(
'form_id' => 9,
'start_field_id' => 1,
'end_field_id' => 2,
'count_field_id' => 3,
'include_end_date' => false
) );

Once you instantiated the class you are finished! If you would like to have this functionality on multiple forms then just create a new instance of the class and fill in the parameters for the new form. That’s it!

Parameter Details

  • form_id: The form ID of the form you would like to apply this functionality to.
  • start_field_id: The ID of the date field that will contain the start date. This field must be a date field and the parameter only holds a single field.
  • end_field_id: This parameter holds the ID of the date field that will contain the forms end date. This field, like the start_field_id field, must be a date field and only holds a single field ID.
  • count_field_id: This parameter holds the ID of the field that will be populated with the calculated number of days between the start date and end date.
  • include_end_date: Defaults to true. Set to this false if you would like to count only “nights” where the start date would be the check-in date and the end date would be the check-out date.

Points of Note

  • This is currently only setup to work with “Date Picker” date fields. Let me know if you need this with other types of date fields in the comments.

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Comments

  2. Hi, this works great. Do you have any suggestions on changing the date for datepicker 2 if datepicker one becomes the same or greater than datepicker2?

    Gravity forms article section: 4. Datepicker 1 + 1 month becomes minDate for datepicker 2 suggests how to make date picker 1 the minimum for datepicker 2 but this breaks the counter if say you set the two date pickers and then move datepicker 1 backwards because datepicker 2 will change. Here’s the article for reference.

    https://docs.gravityforms.com/gform_datepicker_options_pre_init/#3-datepicker-1-becomes-mindate-for-datepicker-2

    Reply

  3. Hi,

    we are getting the following error when trying to install the snippet in the child theme’s function.php:

    Uncaught Error: Class ‘GWDayCount’ not found in wp-content/themes/oceanwp-child-theme-master/functions.php:32 Stack trace:

    0 wp-settings.php(499): include()

    1 wp-config.php(90): require_once(‘/homepages/26/d…’)

    2 wp-load.php(37): require_once(‘/homepages/26/d…’)

    3 wp-admin/admin.php(34): require_once(‘/homepages/26/d…’)

    4 wp-admin/theme-editor.php(10): require_once(‘/homepages/26/d…’)

    5 {main}

    thrown

    Any idea how to troubleshoot this one?

    Reply

  4. Hi

    I did this, all looking fine for me. My next step is, that I have prices for a service, and they vary depend of the amount of days.

    Any idea, how is the best way to calculate and get a number, where the amount per days is vary?

    Regards,

    Simon

    Reply

  5. Hi, how do i add to two separate forms? I attempted to just add another line of this text :

    “new GWDayCount( array( ‘form_id’ => 5, ‘start_field_id’ => 4, ‘end_field_id’ => 8, ‘count_field_id’ => 31, ‘include_end_date’ => false ) );”

    Changing the form id, but it isn’t working on the new form. Am I doing something wrong?

    Reply

  7. What type of field do I need to use to make this work? I tried with a number field but it is not populating.

    FYI, I purchased the 1 perk package (conditional dates) if that has anything to do with it.

    Reply

  8. I want to know if this works with what im trying to do is.

    when a customer select a start date and end date it checks the month if its from january to january then it charges $80 if the date is between january to february then is should charge 80+70 and so on.

    would I be able to do something like this with this ?

    Reply

    • Does it actually matter which months or are you just attempting to calculate the number of months and then the first month is $80, second month is $70, third month is $60, and so on?

  9. Hi, I’m stuck at this step

    Once you instantiated the class you are finished! If you would like to have this functionality on multiple forms then just create a new instance of the class and fill in the parameters for the new form. That’s it!

    What does it mean to instantiate the class?

    Reply

    • Hi Ivonne, instantiate is a big word but all it means is that you’ll be creating a new “instance” of the GWDayCount() class with a set of parameters (aka options) for that specific instance. See the “Standard Usage” usage example.

  10. Hi,

    The snippet works great. But the jQuery script (i.e. window.gwdc) gets added at top of the HTML before DOCTYPE when the gravity form is loaded in a popup using any plugin which throws jQuery not defined error. Do you have any solution for that?

    Thanks, Mou

    Reply

    • Hi Mou, we have made some improvements to how we load scripts in snippets but they have not been implemented here. If you have any PHP experience, here’s an example of how the scripts should be enqueued: http://snippi.com/s/1dj9jke This snippet is in the queue for an update. No definite ETA.

  11. Is it possible to calculate the range between two dates and recalculate the subtotal at checkout page? Yes, we are trying to use it as a simple booking system.

    Reply

    • This snippet would allow you to calculate the number of days between two dates. You could use that in a Product calculation field to calculate a product price based on that number.

  12. Fatal error: Call to undefined function wp_parse_args() in E:\xampp\htdocs\Funeral-Homes-Portal\celi.php on line 20

    Reply

    • Hi Ruairi, Date Time Calculator supports calculating weekdays and weekendDays between two dates but does not support calculating the number of a specific day.

  15. Hi, How do I use this? Not sure I understand the below. Is there an example?

    How do I use this functionality? To use this snippet’s functionality just go directly below the snippet and instantiate the GWDayCount() class. Instantiate is a big word but all it means is that you’ll be creating a new “instance” of the GWDayCount() class with a set of parameters (aka options) for that specific instance.

    Not understanding the above.

    Reply

  16. Dear David

    Thanks for the code!

    1. I get an error when trying to save the functions.php file… Can you kindly help me understand what’s went wrong?

    ” Uncaught Error: Class ‘GWDayCount’ not found in wp-content/themes/oceanwp-child/functions.php:25 “

    1. I didn’t seem to understand what kind of field I should use in the form that will populate the result.

    Best Tal

    Reply

  17. David, I’d like to use this snippet to calculate the difference between two dates: – today – start of an event date I will not use date picker fields as the second date is set and will (in a later form update) be populated using your populate anything perk as it is taken from a clan calendar plugin. Do you have a version of this snippet that works with regular date fields in this manner?

    Reply

    • Ignore the above request. It seems that using the date picker format makes it easier to populate the field dynamically as one input is provided (as opposed different year, month and day fields when the date type is selected). Only weird thing is that apparently a separate filter setting is required to make a datepicker actually read-only when using the relevant perk.

    • Yes, readonly only applies to the manual user input (just like in your browser) by default. Javascript is able to interact with inputs regardless of the readonly attribute so an additional filter is required if you want to disable the datepicker.

    • David, okay thanks for the explanation. I’ll drop the relevant code in my snippets plugin items (nice alternative for functions.php which gets overwritten on theme update or having to struggle with child themes tec.)

  18. David,

    What I want to do is a little complex. Or at least it is for me. I am, sadly, not a coder.

    I want to notify our clients as to when their stuff will be ready. I want to take today’s date and add 21 days to it.

    I want to have something at the bottom of the form, before they submit, that says “Your documents will be created on or before 3_weeks_From_Today”

    Ideally, I would have a single radio button or checkbox that says “I understand my documents will be ready on variable_date.”

    But I realize that’s a probably a tall order!

    Any feedback is greatly appreciated, even if its: “Hire a coder!”

    Thank you in advance.

    Reply

  19. For my project, I needed to modify the code slightly because the javascript being output in this function “function load_form_script( $form )” was preventing my redirect at the end of my form.

    (I’m using Gravity Forms to generate a custom product and add it to the cart – without ajax – and then redirecting to the cart upon completion of the form).

    The solution was to remove the entire chunk of javascript (line 50 to 142) and put it inside the form in a HTML block.

    I also cleaned up the PHP by removing the “self::$script_output = true;” both above and below where the javascript was, and not more “can’t modify headers” error after submitting my form.

    Hope this helps others who run into this issue.

    Reply

  20. When I add the code into my functions file, WordPress get the white screen of dead. Are there some changes needed for WP5?

    Reply

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