# Date Calculator - Days Between Dates, Add/Subtract Days & Age Calculator

> Free online date calculator: days, weeks, months and workdays between two dates; add or subtract to find a date and its weekday; exact age and next birthday.

- URL: https://qilingtools.com/en/date-calc
- Category: Productivity (https://qilingtools.com/en/office)
- Tags: [Date & Time](https://qilingtools.com/en/tags/time), [Productivity](https://qilingtools.com/en/tags/office)
- Last updated: 2026-10-26
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

Three everyday date calculations on one page. Days between: how many days separate two dates, also shown as weeks + days, months + days and years/months/days, plus the number of workdays (Mon–Fri) and weekend days, with an option to include the end date. Add/subtract: move a date forward or back by N days, weeks, months or years and see the resulting date and weekday; month-end dates are clamped correctly. Age: exact age down to the day, total days lived, a countdown to the next birthday, the Chinese zodiac animal (based on Lunar New Year) and the Western star sign. Everything runs in your browser.

## How to use

1. Pick a tab: Days between, Add/subtract or Age
2. Choose the dates (the Today button fills in today), and enter an amount or date of birth
3. Results update instantly: days, weeks, months, workdays, weekday, zodiac and more

## Features

- Days between two dates with week/month/year breakdowns
- Counts workdays and weekend days, optional inclusive end date
- Add or subtract days, weeks, months or years with leap-year handling
- Shows weekday, day of year and ISO week number
- Exact age to the day, days lived and next-birthday countdown
- Chinese zodiac by Lunar New Year, plus Western star sign
- Calendar-day math in UTC, unaffected by daylight saving time

## FAQ

### Does the day count include both the start and end date?

By default it is end date minus start date, so the end day is not counted (1st to 2nd = 1 day). Tick "Include end date" to count both ends, which adds one day — useful for leave or event durations.

### Are public holidays excluded from workdays?

Workdays are Monday to Friday; only Saturdays and Sundays are excluded. Public holidays differ by country and year, so they are not removed automatically — subtract them yourself if you need an exact business-day count.

### What is January 31 plus one month?

When adding months or years, a day that does not exist in the target month is clamped to the month's last day, so Jan 31 + 1 month is Feb 28 (or Feb 29 in a leap year). Adding days or weeks always moves by exact day counts.

### Why doesn't my Chinese zodiac match my birth year?

The zodiac year starts at Lunar New Year, not January 1. Someone born on Feb 9, 2024 (before Lunar New Year) is a Rabbit, while Feb 10, 2024 onward is a Dragon. The tool uses your browser's built-in Chinese calendar to get this right.

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