Calculate the week number of any date and find the beginning and end date of a specific week of any year.

See a Gregorian calendar for this year. 12 Months of Varying Length. The Gregorian calendar is a solar calendar based on a 365-day common year divided into 12 months of different lengths. Eleven months have either 30 or 31 days, while the second month, February, has only 28 days during the common year.

The delay in switching meant that countries followed different calendar systems for a number of years, resulting in differing leap year rules. In the Gregorian calendar, most years that are evenly divisible by 100 are common years, but they are leap years in the Julian calendar.

What is a leap year, and when is the next one? Find out if 2025 is a leap year, how they are calculated, and why we use them.

Years in the Jewish calendar are designated AM to identify them as part of the Anno Mundi epoch, indicating the age of the world according to the Bible. For example, the beginning of the year 2025 in the Gregorian calendar converts to year AM 5785 in the Jewish calendar.

Most years have 52 weeks, but if the year starts on a Thursday or is a leap year that starts on a Wednesday, that particular year will have 53 numbered weeks. These week numbers are commonly used in some European and Asian countries; but not so much in the United States.

When Does the Year Begin? In most regions, the year starts on the New Moon before the Sun enters the zodiac sign of Aries (Meṣa). This happens on or around the day of the March equinox, which marks the beginning of spring in the Northern Hemisphere. Added or Omitted Months

Decades—periods of ten years—begin when the year count ticks over from a year ending with 9 to a year ending with 0. For example, New Year's Day 1980 marked the beginning of the eighties. After all, they are called “the eighties” and not “the eighty-ones,” right?

This is to keep our current calendar aligned with the solar year and astronomical seasons marked by equinoxes and solstices. The 12 Months. The Gregorian calendar consists of the following 12 months: January - 31 days; February - 28 days in a common year and 29 days in leap years; March - 31 days; April - 30 days; May - 31 days; June - 30 days ...

For each year that passes, Islamic dates fall on earlier dates in the Gregorian calendar. It takes 33 years until the Hijri year has cycled through a full Gregorian year and a given Islamic date again falls on the same Gregorian date.