Date Calculator Tool
Calculate date ranges, add/subtract days, and count business days in real-time. Includes Japanese national holidays for accurate business day calculations.
Excluded Holidays List
How to Use
Select Calculation Mode
Choose a tab: "Duration" for days between dates, "Add/Subtract" to add or subtract N days, or "Business Days" to count workdays excluding weekends and holidays.
Enter Dates
Enter start and end dates using the date inputs. Click "Today" for quick input. Set options like "Include start day" or "Business days only" as needed.
View & Copy Results
Results update in real-time as you type. View days, weeks, months, years, weekdays, and Japanese era at a glance. Use "Copy Result" to copy to clipboard.
About Date Calculator
A web tool for calculating date ranges, adding/subtracting days, and counting business days in real-time. Built-in Japanese national holiday data enables accurate business day calculations. All processing happens in your browser - no data is sent to any server.
Features
- 3 Modes in OneDuration calculation, date add/subtract, and business day counting - all in one tool with tab switching.
- Auto Holiday ExclusionAutomatically excludes 16 Japanese national holidays + substitute holidays + citizens' holidays. Equinox dates calculated astronomically.
- Real-time CalculationResults appear instantly as you enter dates. No button clicks needed.
- Japanese Era SupportAutomatically displays Reiwa, Heisei, Showa, Taisho, and Meiji era years.
Use Cases
- Project timeline and deadline calculations
- Calculate resignation and job start dates
- Anniversary countdowns
- Invoice payment due dates (business day basis)
- Contract period day counting