Calendar Facts Calculators

How the Number of Days in Any Month Is Determined

Most months follow a fixed Gregorian-calendar length, but February's day count depends entirely on whether its year is a leap year — the one genuinely variable case in an otherwise predictable pattern.

Leap Year Rules Explained: Why 1900 Wasn't a Leap Year but 2000 Was

The full Gregorian leap-year rule has three layers, not one — divisible by 4 (leap), except century years (divisible by 100), which are leap only if also divisible by 400 — which is exactly why 2000 was a leap year but 1900 and 2100 are not, despite all three being divisible by 4.

What Is a Fiscal Year in India? (And Why It Doesn't Match the Calendar Year)

India's fiscal year runs from 1 April to 31 March, not January to December — so a date like 15 January 2027 falls in fiscal year 2026-27, not "2027" as the calendar year alone might suggest, and getting this wrong is a common source of confusion when filling out tax forms or reading financial reports.

Why a Date Calculation's Result Depends on Which Month It Lands In

Adding the identical 30 days to two different starting dates lands one result in a 28-day February and the other in a 31-day October — the same day count, landing in genuinely different-length months.