Date Calculator

What is Date Calculator?

Free date calculator. Find the exact difference between two dates, add or subtract days from a date, and calculate business days. Date and time tools that support Indian Standard Time (IST) and the Indian calendar. TekPulse's Date Calculator is completely free — no signup, no ads in results, and no data stored on our servers.

How to Use Date Calculator Online

1. Choose your mode: Date Difference (find days between two dates) or Date Addition/Subtraction
2. For Date Difference: select a start date and an end date
3. View the difference in years, months, weeks, and days
4. For Date Addition: enter a starting date and add or subtract a number of days, weeks, or months
5. Business day calculations exclude weekends; toggle "Include weekends" to count all days

Date Calculator Formula & Calculation

The simple day-count figure comes from converting both dates to milliseconds since the Unix epoch, taking the difference, and dividing by 86,400,000 (the number of milliseconds in a day) — this automatically accounts for leap years because each actual calendar day, including 29 February in a leap year, is one full day in the millisecond count.

The "Years, Months, Days" breakdown is calculated differently: it subtracts year, month, and day components separately, then borrows from the next higher unit when a component goes negative (e.g. if the end day-of-month is smaller than the start day-of-month, it borrows a month's worth of days — using the actual number of days in that calendar month, so it correctly handles 28, 29, 30, or 31-day months).

Example: From 15 Jan 2026 to 1 Mar 2026 → Total days = 45. Y/M/D breakdown: 0 years, 1 month, 14 days (borrowing because day 1 < day 15, so it takes 28 days from February 2026 — not a leap year — and reduces the month count by one).

Key Factors That Affect Your Result

1. Leap years — Automatically handled because the day-count uses real calendar dates; a range spanning 29 February is counted correctly without any special-case logic needed from the user.
2. Business days — The tool also reports business days by excluding Saturdays and Sundays only; like the dedicated Working Days tool, it does not account for public holidays.
3. Add/Subtract by month or year — Adding "1 month" to 31 January lands on 28 or 29 February (JavaScript's Date object auto-adjusts overflow), not on a non-existent "31 February" — worth knowing if you're calculating recurring monthly deadlines from a month-end date.

Why Use TekPulse Date Calculator?