How to Subtract One Year from a Date using Acrobat JavaScript
Question details
The user needs to use JavaScript in an Adobe Acrobat PDF form to automatically populate a target field with a date exactly one year earlier than the date entered in a source field.
- Product
- Adobe Acrobat
- Device & OS
- not provided
- Scenario
- Creating or editing a fillable PDF form that requires automated date calculations based on user input.
- Observed behavior
- The target field needs to dynamically calculate and display a date that is one year prior to the date inputted by the user in the source field.
Ensure you have a PDF editing tool that supports form field creation and JavaScript validation, such as Adobe Acrobat Pro. Identify the exact field names for both your source date field and target date field before applying the script.
Use a Validation Script on the Source Date Field
Add a custom JavaScript validation script to the source field so the target field updates automatically whenever a new date is inputted.
This method uses Acrobat's built-in JavaScript engine to scan the inputted date string, mathematically subtract one year, and print the new date into your designated target field.
Open your PDF document in Adobe Acrobat and select the 'Prepare Form' tool from the right-hand pane.
Right-click the source date field (where users will type the initial date) and select 'Properties' from the context menu.
In the Text Field Properties dialog box, click on the 'Validate' tab.
Select the 'Run custom validation script' option and click the 'Edit' button. Paste the following code, ensuring you replace 'WSD' with your actual target field name: if (event.value == "") this.getField("WSD").value = ""; else { var d = util.scand("mm/dd/yyyy", event.value); d.setFullYear(d.getFullYear() - 1); this.getField("WSD").value = util.printd("mm/dd/yyyy", d); }
Click 'OK' to save the script, close the properties window, and exit form editing mode. Test the script by entering a date like '12/31/2023' into the source field to confirm the target field automatically populates with '12/31/2022'.
Set a Field to One Year from Today's Date
Use this alternative script if you need a field to automatically display a date exactly one year from the current day upon opening the document or clicking a button.
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Frequently Asked Questions
Why is the target field not updating when I enter the date?
This usually happens if the target field name in the JavaScript (e.g., 'WSD') does not perfectly match the actual name of the field in your form. Ensure the field names are case-sensitive and match exactly.
How do I change the date format in the Acrobat JavaScript?
You can change the date format by modifying the parameters in the util.scand and util.printd functions within the script. For example, you can change 'mm/dd/yyyy' to 'dd/mm/yyyy' depending on your regional format requirements.
Can I use a similar script to add days instead of years?
Yes. Instead of using the d.setFullYear() method, you can use d.setDate(d.getDate() + 30); to mathematically add 30 days to the date entered in the source field.
