To calculate date difference: 1) Enter your start date, 2) Enter your end date, 3) Choose calculation units (days, weeks, months, etc.), 4) View results. Our tool automatically accounts for leap years and varying month lengths. You can also exclude weekends or specific days if needed.

Yes! Use our date arithmetic feature: 1) Enter your base date, 2) Select "Add" or "Subtract", 3) Specify the number of days/weeks/months/years, 4) View the resulting date. This is useful for calculating deadlines, expiration dates, or future events.

We accept all common formats: MM/DD/YYYY, DD/MM/YYYY, YYYY-MM-DD, Month D, YYYY (e.g., January 1, 2023). The tool automatically detects your region's preferred format. You can also use our calendar picker to avoid manual entry errors.

For business day calculations: 1) Enable "Workdays Only" option, 2) Set your work week (default M-F), 3) Add custom holidays if needed, 4) View business days count. The tool highlights weekends and holidays in the calendar view for easy verification.

Our age calculator provides: 1) Full years completed, 2) Additional months, 3) Remaining days, 4) Total days lived, 5) Next birthday countdown. For precise age calculations, you can even include the time of birth in the input fields.

Premium version supports: 1) Gregorian (default), 2) Lunar, 3) Hebrew, 4) Islamic (Hijri), 5) Persian calendars. Convert dates between systems or perform calculations directly in alternative calendars. Great for cultural or religious date planning.

For event countdowns: 1) Enter today's date (auto-detected), 2) Enter the future event date, 3) Choose display format (days only or breakdown), 4) Save as a shareable countdown link. The tool updates automatically when revisited.

Yes! Specialized modes include: 1) Pregnancy calculator (LMP or conception date), 2) Gestation periods for animals, 3) IVF calculations, 4) Trimesters breakdown. These use medical standards (280 days for human pregnancy) with adjustable parameters.

For recurring events: 1) Set your start date, 2) Choose interval (days/weeks/months/years), 3) Specify frequency (every 2 weeks, etc.), 4) Set end date or occurrence count, 5) Generate complete schedule. Export as calendar file or printable list.

Common issues: 1) Wrong date format interpretation (DD/MM vs MM/DD), 2) Timezone differences, 3) Daylight saving changes, 4) Browser locale settings. Try: using the calendar picker, checking your device's region settings, or manually verifying one calculation.

Very old dates may fail if: 1) Before calendar system changes (1752 switch in UK/US), 2) Exceeding JavaScript date limits (year 275760), 3) Invalid for the selected calendar system. For historical research, use our specialized Julian/Gregorian converter.

Time calculations are precise to the second, accounting for: 1) Leap years, 2) Daylight saving changes, 3) Timezone offsets, 4) Leap seconds. For absolute precision over long periods, enable "Astronomical Mode" which uses NASA algorithms.