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Video walkthrough

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Calculate Days Between Dates in Gravity Forms (Incl. Working Days)
Video walkthrough: counting calendar days and working days between two Gravity Forms date fields with Date/Time Calculator. Watch on YouTube

The Gravity Forms Date/Time Calculator Premium Add-on enables real-time mathematical calculations using native Date and Time fields directly inside Gravity Forms. Whether you need to compute elapsed calendar days, calculate client age from a date of birth, filter out weekend days for project SLAs, or charge dynamic rental rates based on duration, this add-on executes accurate client-side and server-side arithmetic without complex custom JavaScript or expensive middleware.

Pillar 1: Overview & Key Capabilities

By default, Gravity Forms calculation formulas only support standard Number and Product fields. The Date/Time Calculator Add-on bridges this gap by automatically converting calendar dates and times into standardized timestamps and duration units. Key capabilities include:

• Full Arithmetic Math: Add, subtract, and multiply date and time fields within standard calculation formulas.
• Automated Age Computation: Instant calculation of a person’s current age using the {field_id:age} modifier.
• Business Days vs. Weekend Days: Count working days (Monday–Friday) or weekend days (Saturday–Sunday) between any two dates using {weekdays:...} and {weekendDays:...}.
• Flexible Output Units: Output differences seamlessly in Seconds, Minutes, Hours, Days, Weeks, or Months.
• Dynamic Duration-Based Pricing: Multiply booking or rental durations directly against hourly or daily rates.
• Real-Time Frontend Evaluation: Formulas update instantly in the user’s browser as dates and times are selected.

Pillar 2: System Requirements & Installation

Before installing the add-on, ensure your hosting environment meets the following specifications:

• WordPress 6.0 or higher.
• Gravity Forms 2.5 or higher.
• PHP 7.4 or higher (fully compatible with PHP 8.1, 8.2, and 8.3).

To install the plugin:

1. Log into your GravityExtra Account and download the plugin ZIP archive.
2. Navigate to Plugins → Add New → Upload Plugin in your WordPress admin dashboard.
3. Select the downloaded ZIP file and click Install Now, then click Activate Plugin.

Pillar 3: Step-by-Step Configuration Guide

Follow these detailed steps to incorporate date and time calculations into your forms:

Step 1: Add Date and Time Input Fields

Open your form in the Gravity Forms editor. Drag and drop your desired Date or Time fields into the form canvas. For instance, add a “Start Date” (or “Birth Date”) and an “End Date” (or “Target Date”).

Step 2: Add a Number or Total Field and Enable Calculation

Add a standard Number or Total field where you want the calculated result to appear. In the field settings on the right panel, check the Enable Calculation checkbox.

Step 3: Select Your Desired Output Unit

Under the field calculation settings, locate the Unit Calculator setting. Choose how you want the duration converted and displayed: Days, Hours, Minutes, or Seconds.

Step 4: Build Your Calculation Formula

Use standard arithmetic operators and merge tags to define your formula. You can subtract two dates ({End Date:2} - {Start Date:1}), use modifiers like :age, or leverage working days functions.

Step 5: Configure Age Calculation Formula

To calculate a user’s age from a Birth Date field, append the :age modifier to the date merge tag. For example, {Birth Date:1:age} automatically calculates age in completed years.

Step 6: Configure Working Days and Weekend Days Formulas

To count working business days or weekend intervals between two date fields, use the specialized function tags: {weekdays:{Start Date:1},{End Date:2}} or {weekendDays:{Start Date:1},{End Date:2}}.

Pillar 4: Merge Tag & Formula Syntax Reference

Below is the complete reference guide for supported merge tags and calculation syntax:

Pillar 5: Practical Real-World Implementation Recipes

Recipe 1: Equipment Rental Pricing with Dynamic Day Rates

To compute total rental charges based on selected pickup and return dates with a $50/day fee and $100 deposit:

(({Return Date:3} - {Pickup Date:2}) * 50) + 100

Recipe 2: Legal & Healthcare Age Verification Gate

To verify if an applicant meets the minimum age requirement of 18 years:

1. Create a Number calculation field labeled “Applicant Age” with formula: {Date of Birth:1:age}.
2. Add a Section Break or Consent field with conditional logic: Show if Applicant Age is greater than or equal to 18.
3. Add an alert message: Show if Applicant Age is less than 18.

Recipe 3: Project Delivery SLA Estimator (Business Days Only)

To quote project delivery costs based solely on working business days at $250/day:

{weekdays:{Start Date:1},{Delivery Date:2}} * 250

Pillar 6: Common Pitfalls & Troubleshooting

• Negative Duration Results: If a user selects an End Date that precedes the Start Date, standard subtraction produces a negative number. Use Gravity Forms conditional logic or the Date Range Selection Add-on to enforce that End Date must be greater than Start Date.
• Time Field 12-Hour vs. 24-Hour Formats: The add-on natively handles AM/PM modifiers when converting time inputs to timestamps. Ensure both hour and minute subfields are filled for valid calculations.
• Browser Cache on Field Edits: When modifying calculation formulas in the form editor, clear your browser cache and purge site object cache (wp cache flush) so updated JavaScript recalculation scripts load fresh.

Pillar 7: Get the Add-on