Tools To India

Date Calculator

Pick a starting date, choose how much time to add or subtract, and see the resulting date and weekday.

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The result updates as you type. Nothing you enter is saved, sent to a server or shared.

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How this calculator works

Adding time to a date is straightforward for days and weeks and surprisingly contentious for months. What is 31 January plus one month? There is no 31 February, so something has to give.

This calculator clamps rather than rolls over: 31 January plus one month gives 28 February, or 29 February in a leap year. Rolling over would give 3 March, which is almost never what anyone means. Clamping matches how contracts, notice periods and administrative deadlines are normally read.

The order of operations matters too. Years and months are applied first, the result is clamped, and then weeks and days are added. Doing it the other way round would produce different answers for the same inputs.

The weekday of the result is shown because it is frequently the point of the exercise — a deadline that lands on a Sunday usually moves.

The formula

Order of operations

1. Apply years and months, clamping the day to the target month’s length 2. Add or subtract weeks and days as a plain day count 3. Report the resulting date and weekday

Worked example: 90 days from 15 January 2026

Finding the date 90 days after 15 January 2026 — a common question for notice periods and cheque validity.

Step-by-step calculation for the worked example
Starting date15 January 2026
Days remaining in January16
Through February (28 days)44 days used
Through March (31 days)75 days used
Remaining days into April15
Resulting date15 April 2026
Day of the weekWednesday

Ninety days from 15 January 2026 is 15 April 2026. Note that this is not the same as three months, which would also be 15 April here only by coincidence — from 30 November, 90 days and 3 months give different answers.

Things worth knowing

  • "Three months" and "90 days" are not the same thing, and contracts sometimes use them interchangeably by mistake. Check which one your document actually specifies.
  • Month-end dates are clamped, not rolled over. 31 January plus one month is 28 or 29 February, never 2 or 3 March.
  • Cheques in India are valid for three months from the date of issue. Use the months field rather than 90 days for that calculation.
  • If a deadline falls on a Sunday or a public holiday, many rules move it to the next working day. This calculator gives the raw date; check the applicable rule for what happens next.

Frequently asked questions

What is 31 January plus one month?
28 February, or 29 February in a leap year. This calculator clamps to the last day of the target month because that is how contracts, notice periods and administrative deadlines are normally interpreted. Rolling over to 3 March would be arithmetically defensible and almost always wrong in practice.
Is 90 days the same as three months?
Only sometimes. Three months from 15 January is 15 April, which happens to be 90 days. Three months from 30 November is 28 February, which is 90 days — but three months from 31 May is 31 August, which is 92 days. If a document specifies days, count days; if it specifies months, count months.
How long is a cheque valid in India?
Three months from the date written on the cheque. Use the months field rather than entering 90 days, since the two can differ by a couple of days depending on the month.

Sources

Every figure on this page is traceable to the official source below. If a source has changed since the date shown, please tell us and we will correct it.