A half-birthday calculator determines the exact date and time that occurs six months after a person’s birth date, and visualizes the result.

How to Use the Half-Birthday Calculator

This practical half-birthday calculator is designed to visualize the birth date and its corresponding half-birthday. It helps users quickly find the date exactly six months after a birth date, see how many days remain until that milestone, and view an interactive timeline.

Why a half-birthday matters

Half-birthdays are a fun way to celebrate milestones, plan small events, or track age-related schedules for children and adults alike. Unlike annual birthdays, half-birthdays fall midway through the year and can be useful for scheduling tests, checkups, or simply sending a reminder. This calculator removes manual arithmetic and calendar guesswork.

What the calculator does

Enter a birth date and the calculator returns the half-birthday date, the day of the week, and how many days remain until that date from today. It also renders a Plotly.js timeline with two markers: the original birth date and the half-birthday. Hover interaction reveals exact dates and relative spacing.

Key features

• Accurate six-month addition that handles month length differences and leap years.
• Responsive layout sized for common WordPress content columns (max-width 720px).
• White background and simple styling so it blends into most themes.
• Interactive Plotly visualization with tooltips and zoom.
• Copyable result and friendly labels for accessibility.

How the calculation works

The script reads the selected birth date, creates a JavaScript Date object, and adds six months by increasing the month value. JavaScript’s date handling correctly manages month overflow and leap-year adjustments. The calculator also computes the difference in days between today and the half-birthday, and displays a friendly countdown. The Plotly timeline is built from two points and automatically scales to the available container width.

Accessibility and responsiveness

Inputs use semantic labels for screen readers and a sufficiently large font. The container uses width:100% with max-width:720px so it will sit comfortably between sidebars on most themes. The Plotly chart is responsive and will redraw when the window resizes. Buttons include clear labels and keyboard-accessible events so the tool is usable without a mouse.

Customization tips

You can adjust max-width to match your theme’s content column. Change the background color by editing the CSS in the provided snippet. To localize date formats or text, edit the label strings. If you prefer a different visualization, swap the Plotly timeline for a simple calendar highlight or a Gantt-style bar. Consider swapping Plotly’s CDN for a hosted or self-hosted copy if you require strict content security policies.

Step-by-step walk-through

1. Open the page or post editor in WordPress and add a Custom HTML block where you want the calculator to appear.
2. Paste the HTML/JavaScript code snippet provided above into the block. The snippet includes a Plotly CDN link and an inline script. If your editor strips script tags, use a code insertion plugin or add the scripts in your theme’s header.
3. Save and view the page. Select a birth date using the date picker. The half-birthday is calculated instantly and appears in a readable format with the day of the week.
4. Inspect the Plotly chart beneath the inputs. Hover the markers to see exact timestamps and zoom if needed. Use the copy button to copy the calculated date to the clipboard.

Troubleshooting tips

• If the date doesn’t appear, open your browser console to check for JavaScript errors.
• If the Plotly graph does not load, confirm the CDN is reachable and not blocked by your site’s content security policy.
• On older phones the date picker may fall back to a plain text entry. Ensure users enter ISO format (YYYY-MM-DD) or use a JS date polyfill if necessary.

Example use cases

• Parents planning a small celebration for a child’s half-year milestone.
• Teachers scheduling mid-year assessments relative to student age.
• Anyone curious about their half-birthday or wanting to send a greeting.

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FAQ

What is a half-birthday?

A half-birthday is the day six months after your birth date.

Does it account for leap years?

Yes. The calculator relies on JavaScript Date arithmetic which correctly handles leap days when adding months.

Can I change the size to fit my theme?

Yes. Modify the CSS max-width value in the code to match your theme’s content column width.

Do I need a plugin to run Plotly?

You do not necessarily need a plugin, but some WordPress setups block script tags. If scripts are blocked, use a plugin that allows safe script insertion or enqueue the CDN via your theme’s functions.php.

Can this be used for groups or multiple dates?

The current version handles a single date input. With small changes you can accept multiple dates and render multiple markers in Plotly.