Calendar
View the current month calendar. See today highlighted, navigate between months, and keep track of upcoming dates.
Date Calculator
On This Day
Notable events that happened on this date in history.
Calendar
The calendar is one of humanity's oldest and most important inventions. From the stone circles of Neolithic times to the digital calendars on our phones, the need to track days, months, and seasons has been a constant throughout history.
The Gregorian calendar, which is the calendar in use throughout most of the world today, was introduced by Pope Gregory XIII in October 1582. It replaced the Julian calendar, which had been in use since 45 BC. The Julian calendar had a simple leap year rule (one leap year every four years), but this made the average year slightly too long, causing the calendar to drift by about one day every 128 years. By the 16th century, the calendar was about 10 days out of alignment with the solar year. The Gregorian reform corrected this by skipping 10 days and introducing a more precise leap year rule.
A month is approximately the length of one lunar cycle, which is about 29.5 days. However, the 12 months in the Gregorian calendar vary in length from 28 to 31 days, and they no longer align precisely with lunar phases. Some calendars, such as the Islamic Hijri calendar, remain purely lunar, with months that follow the actual phases of the Moon. The Hebrew calendar is lunisolar, combining lunar months with occasional leap months to stay in step with the solar year. The Chinese calendar is also lunisolar and is used to determine traditional festivals like Chinese New Year. The Hindu calendar system is remarkably complex, with multiple regional variations used across India for religious and cultural observances.
The adoption of the Gregorian calendar was not instant — it took centuries. Catholic countries in Europe switched in 1582, but Protestant nations resisted for over 150 years. Britain and its colonies adopted it in 1752, Russia in 1918, and Greece in 1923. Japan adopted the Gregorian calendar in 1873 as part of the Meiji modernization, and most East Asian countries followed during the early 20th century. Today, even countries that use the Gregorian calendar for civil purposes often maintain traditional calendars for religious and cultural events.
Seasons play a significant role in how we experience the calendar year. In the Northern Hemisphere, spring begins around March 20, summer around June 21, autumn around September 22, and winter around December 21. These dates are determined by the solstices and equinoxes, which mark the points when Earth's axial tilt is most inclined toward or away from the Sun, or when day and night are approximately equal in length.
Digital calendars have transformed how we organize time. Standards like iCalendar (iCal, specified in RFC 5545) and CalDAV allow calendars to synchronize across devices and platforms. When you create an event in Google Calendar or Apple Calendar and it appears on your phone seconds later, these protocols are working behind the scenes. The .ics file format, which encodes calendar events as plain text, is the universal lingua franca for sharing events via email or links.
Our calendar page displays the current month in a clear, easy-to-read grid format. Today's date is highlighted so you can orient yourself at a glance. You can navigate forward and backward through the months to plan ahead or look back. The week starts on Sunday or Monday depending on your locale. An "On This Day" section shows notable historical events that occurred on the current date, adding a layer of context and interest to your daily view.
Whether you are planning appointments, checking how many weekdays remain in the month, or simply want a visual overview of the weeks ahead, this interactive calendar is a practical everyday tool.
FAQ
Why do months have different numbers of days?
The lengths of the months were established by Roman rulers and have remained largely unchanged since the Julian calendar reform in 45 BC. The variation (28 to 31 days) is a historical artifact rather than an astronomical necessity.
What is the Gregorian calendar?
The Gregorian calendar is the civil calendar used in most of the world. It was introduced by Pope Gregory XIII in 1582 to correct the drift of the Julian calendar. It uses a refined leap year rule to keep the calendar year aligned with the solar year.
When do the seasons start?
In the Northern Hemisphere, spring begins around March 20, summer around June 21, autumn around September 22, and winter around December 21. These dates are based on equinoxes and solstices. In the Southern Hemisphere, the seasons are reversed.
Does the week start on Sunday or Monday?
It depends on regional convention. In the United States and some other countries, calendars typically start on Sunday. The international standard ISO 8601 defines Monday as the first day of the week, which is the norm in most of Europe and many other countries.
How many weeks are in a month?
Most months span parts of four or five weeks. February in a non-leap year starting on Monday is the only month that fits exactly into four weeks (28 days). All other months have 29 to 31 days, so they overlap into a fifth week.
What other calendar systems are still in use today?
Many calendar systems coexist with the Gregorian calendar. The Islamic Hijri calendar is a purely lunar calendar with 354 or 355 days per year, used to determine Islamic holidays like Ramadan. The Hebrew calendar is lunisolar and governs Jewish holidays. The Chinese calendar, also lunisolar, determines festivals like Chinese New Year. The Hindu calendar has many regional variants used across India. Ethiopia uses the Ge'ez calendar, which is 7-8 years behind the Gregorian calendar. Iran and Afghanistan use the Solar Hijri calendar.
How do digital calendars sync across devices?
Digital calendars use open standards for synchronization. CalDAV is the protocol that lets your calendar app communicate with a server to keep events in sync. The iCalendar format (RFC 5545) defines how events are encoded, and .ics files serve as the universal format for sharing events. When you receive a calendar invite via email, it is typically an .ics file that your calendar app can import directly.