Date Difference Calculator

WHAT IT DOES

Date Difference Calculator gives you complete control over date calculations. Enter two dates and see the exact difference broken down into years, months, days, weeks, total days, total hours, total minutes, and total seconds. But that's not all — the panel also includes a date arithmetic tool that lets you add or subtract a specified number of days, months, or years from any base date, showing you the resulting date instantly. Whether you are calculating project timelines, counting down to an event, or performing date-based business calculations, this tool has you covered.

WHERE IT RUNS

This script runs on every website you visit. Whether you are planning projects on productivity platforms, calculating delivery dates on e-commerce sites, tracking deadlines on project management tools, or simply figuring out how many days until a special occasion, the panel is always available. It works alongside your existing tools without interfering with your workflow.

HOW TO USE

For date difference: Select the first date using the date picker, select the second date, and the results update automatically. Use the "Swap Dates" button to quickly reverse the order. The main result shows the difference in years, months, and days, with detailed breakdowns below including weeks, total days, total hours, total minutes, and total seconds. For date arithmetic: Select a base date, choose the number of days, months, or years to add or subtract, select the operation (+ or -), and click "Calculate." The result shows the original date, the operation performed, and the new date. Click any history entry to reload previous date pairs for quick comparisons. Use the "Copy Result" button to copy both the difference and arithmetic result to your clipboard.

THE PRECISE DATE DIFFERENCE MECHANISM

Date Difference Calculator uses a calendar-aware algorithm that correctly handles variable month lengths, leap years, and edge cases like dates at month boundaries. The difference calculation subtracts the earlier date from the later date by first computing the year difference, then adjusting for month and day borrows based on the actual number of days in each month. The total time units (weeks, days, hours, minutes, seconds) are derived from the exact millisecond difference between the two dates, ensuring precision down to the second. For date arithmetic, the calculator adds or subtracts the specified amount using native JavaScript Date methods that automatically handle month overflow, day-of-month adjustments, and leap year transitions correctly. This dual-mode approach gives you both the human-readable calendar difference and the precise machine-level time measurements.

THE PANEL

The panel is fully draggable and remembers its position per site. It minimizes to a compact floating bubble when collapsed. All calculation history persists across browser sessions using GM_setValue storage. Press the Escape key to close the panel. The panel automatically focuses the first date input field for quick keyboard entry.

PLEASE NOTE

This script requires the free BotGentz extension to run. Date calculations assume the Gregorian calendar and are accurate for dates from 1900 onward. Always verify critical business dates with your official systems. Websites change their structure and behavior over time; if any functionality stops working, the script may need an update. No user data is sent anywhere — all calculation history and settings are stored locally in your browser. The script never reads or modifies password, hidden, or file input fields.