Recurring Date Calculator

WHAT IT DOES

Recurring Date Calculator is a browser extension that calculates a list of recurring dates based on a starting date, recurrence pattern, and number of occurrences. You can choose from daily, weekly, monthly, or yearly recurrence patterns, and optionally filter weekly recurrences to weekdays only (skipping Saturdays and Sundays). The tool displays the generated dates in a clear, numbered list with both formatted and ISO date formats, and allows you to copy all dates to your clipboard with one click. The tool also saves your last 20 calculations as history for quick reloading. The tool is ideal for project managers, event planners, subscription managers, payroll administrators, and anyone who needs to generate recurring date schedules.

WHERE IT RUNS

Recurring Date Calculator runs on any webpage, overlaying a floating panel that does not interfere with page content. It operates entirely in your browser as a lightweight userscript, using JavaScript's Date object for date calculations. It works on any page, whether static or dynamic, with no external dependencies. All calculation history is stored locally using GM_setValue—no data is ever sent to any server.

HOW TO USE

After installation, open the floating panel by clicking the extension icon. Enter a start date in the "Start date" field using YYYY-MM-DD or MM/DD/YYYY format (the current date is pre-filled). Select a recurrence pattern from the dropdown: Daily, Weekly, Monthly, or Yearly. Enter the number of occurrences to generate (1-100). Optionally check "Weekdays only" to skip weekends when using weekly recurrence. Click the Calculate button to generate the dates. The results appear in a numbered list showing each date with its day of the week and ISO format. Click Copy All to copy all generated dates to your clipboard as a list. Your calculations are saved in the History section—click the ↺ button next to any history entry to reload those parameters and recalculate.

REAL MECHANISM — WHY THIS WORKS

Most date calculators rely on external APIs or manual spreadsheet formulas that require complex setup. Recurring Date Calculator uses a deterministic date generation algorithm implemented entirely in JavaScript. The engine takes a starting date, a recurrence interval, and a count, then generates a sequence of dates by advancing the date object by the interval for each step: +1 day for daily, +7 days for weekly, +1 month for monthly (using JavaScript's setMonth which handles month overflow correctly), and +1 year for yearly. For weekly recurrence with weekdays-only filtering, the engine generates dates one day at a time and checks if the day of week is Saturday (6) or Sunday (0), skipping those days and continuing until the requested number of valid dates is generated. A safety counter prevents infinite loops. Each generated date is stored as a new Date object to avoid mutation issues. The results are displayed using the browser's local timezone. History records the parameters of each calculation, allowing quick reloading. This approach ensures accurate, fast, and fully private recurring date generation without requiring any external services or network access.

THE PANEL

The floating panel is fully draggable and remembers its position per site, snapping to the edges of the viewport when dragged near them. You can collapse the panel to a small icon to minimize screen distraction and expand it back with a single click. The panel is resizable from the bottom-right corner, giving you more space to view generated dates. Press the Escape key to close the panel instantly. The panel remains open across page navigation within the same domain, maintaining your current view state. All preferences—panel position and calculation history—are saved globally for a seamless experience.

PLEASE NOTE

Recurring Date Calculator requires the free BotGentz extension to be installed and enabled, as it relies on the cross-extension messaging API provided by BotGentz for DOM access permissions. The date parser supports YYYY-MM-DD, MM/DD/YYYY, and DD.MM.YYYY formats. All dates are calculated in your browser's local timezone. The maximum number of occurrences is 100 to prevent excessive calculations. Calculation history is stored locally and limited to 20 entries. No date data or usage information is ever sent to any server. The extension does not read, store, or transmit any personal information. It only calculates and displays dates locally at your request.