Hours and Minutes Calculator

Online Hours Calculator

We get around easily enough by calculating numbers on a calculator. But the number of hours is not always easy to calculate. There are 24 hours in a day, 28 to 31 days in different months, and 365 or 366 days in a year. Have you ever asked yourself these questions:

• How long will a particular event last?
• How many hours are left before midnight or another specific time?
• How many hours are left between two events, several days, weeks, or even months apart?

The Hours Calculator can help answer such questions.

Hours Calculator

The standard Hours Calculator has a start time and an end time. So, you can input any time as your starting point and any time of the day or evening as your ending point. Once you hit the "Calculate" button, you will get information on exactly how many hours there are between those two points.

So, if you were to enter 8:30 a.m. and 5:30 p.m., you could instantly determine how much time you need to spend at work during the day. In this case, that number is nine hours. However, the Hours Calculator also tells you the number of minutes you have between the two points.

Hours Between Two Dates Calculator

What if you wanted to find out the number of hours between two times more than 24 hours apart? Would you like to know how many hours passed between some historical dates? That's where the extended Hours Calculator function comes in handy.

Like the standard version, it has a Start Time and End Time. However, for this calculator, you can set the hours, time of day, date, and year of each, then calculate the number of hours in between. This particular calculator has several outputs, including:

• days, hours, and minutes;
• hours and minutes;
• hours;
• minutes.

Problems This Calculator is Designed to Solve

The standard Hours Calculator is ideal for determining how long an event might last. You might be attending your cousin's graduation, which is slated to last from 11:45 a.m. to 4:00 p.m. By entering these numbers in the calculator, you can see that the event will last four hours and fifteen minutes, 4.25 hours, or 255 minutes altogether.

Of course, you can also look up the duration of events that took place in the past. For instance, let's say you were writing a book about WWII and wanted to make an impactful statement regarding how long the attack on Pearl Harbor lasted.

We know from military recordings that the attack began at 7:48 a.m. and ended just after 9:00 a.m. Using those times, we can calculate that Pearl Harbor was under attack for just 1 hour and 12 minutes, 1.2 hours, or 72 minutes altogether.

The Measurement of the Hour in History

From Antiquity to Modern Times

Ancient Greeks divided the time from sunrise to sunset into 12 "seasonal hours." Initially, only the day was divided into 12 seasonal hours, and the night was divided into 3 or 4 night hours. By the Hellenistic period, the night was also divided into 12 hours. Day and night were first divided into twenty-four hours by the Greek astronomer and mathematician Hipparchus of Nicaea, who lived between 120 and 190 B.C.

Medieval astronomers, such as the Iranian mathematician Abu Rayhan Muhammad ibn Ahmad al-Biruni and the French scholastic Johannes de Sacrobosco, divided the hour into 60 minutes. Each of which consisted of 60 seconds. Initially, the hexadecimal system was used by Babylonian astronomers.

In medieval Europe, Roman clocks continued to be noted on sundials. But the more important time measurement units were the canonical clocks of the Orthodox and Catholic churches. During daylight hours, the canonical clocks followed the pattern established by the bells of Roman markets and local churches. They rang around 6 a.m., around 9 a.m., at noon, around 3 p.m., and at 6 p.m., or sunset.

During the French Revolution, universal decimalization of measures was introduced. Time was also reformed between 1793 and 1795. Under the new provisions, the French hour was 1⁄10 of a day and divided formally into 100 minutes. The official use of such a system did not last long. The law of 1795 brought back to France the former system of division of time, which we use today.

The metric system uses the second to measure time. Since 1952, the second has been defined in terms of the rotation of the Earth. In this system, the hour is expressed in seconds and consists of 3,600 seconds.

Counting hours

There have been many ways of counting hours in history. We count the day from midnight, but that was not always the case in ancient times.

Sunrise and sunset are the most prominent points in the twenty-four hours. Therefore, in ancient times, it was much easier for most people in early societies to start counting at this time. This issue is no longer a problem with the advent of accurate clocks and modern astronomical equipment.

Countdown from dawn

In ancient and medieval cultures, the counting of clocks usually began at sunrise. People's daily routines in ancient times often started when there was enough light.

Sunrise marked the beginning of the first hour, midday was at the end of the sixth hour, and sunset was at the end of the twelfth hour. The length of the hours varied according to the seasons.

In the Northern Hemisphere, especially in the more northern latitudes, the summer daylight hours are longer than the winter hours. Each daylight hour was one-twelfth of the time between sunrise and sunset. These hours of variable length were known as temporary, unequal, or seasonal hours.

This system is also called the Talmudic hour. The Talmudic hour is one-twelfth of the time elapsed from sunrise to sunset, so the daylight hours are longer than the night hours in summer and the opposite in winter.

Countdown from Sunset

In the so-called "Italian time," the first hour begins with the sunset bell. The hours were numbered from 1 to 24. People used this system of division of time in Italy in the XIV-XVIII centuries.

Changes in the duration of daylight and dark hours in different seasons created significant differences. In Lugano in December, the sunrise occurred at 14, and noon was at 19. In June, the sunrise occurred at 7 and noon at 15.

This way of calculating time was advantageous for people who worked until sundown. Everyone could quickly know how much time they had left before the end of the day. This system was also used in Poland and Bohemia until the 17th century.

The Islamic day begins with sunset. Maghrib, the day's first prayer, is performed immediately after sunset and before dusk.

Countdown from Noon

Until 1925, astronomers counted hours and days from noon for many centuries. The noon was the simplest solar event that people could accurately measure. The astronomeers also used this method to calculate the dates of the Julian calendar.

Countdown from Midnight

In modern times, the clock starts counting at midnight. We can use both the 12-hour and 24-hour systems to calculate time.

The 12-hour clock is a timekeeping system in which the 24 hours of the day are divided into two periods. The first period lasts until noon and is denoted by the letters a.m. (from the Latin ante meridiem, which translates to "before noon"). The second period lasts after noon and is denoted by the letters p.m. (from Latin "post meridiem", which translates as "after noon").

Each period consists of 12 hours. They are numbered as: 12 (stands for 0), 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.

The 12-hour clock system was developed in the second millennium B.C. The 12-hour system is dominant in countries that were part of the former British Empire, such as Great Britain, the Republic of Ireland, the United States, Canada (except Quebec), Australia, New Zealand, South Africa, India, Pakistan, and Bangladesh. But other countries also follow this convention, such as Mexico and the Philippines.

The 24-hour clock system is popular in the United States and many other countries. It is also known as "military time." On a 24-hour clock, the day lasts from midnight to midnight and is divided into 24 hours. Time is indicated by the hours (and minutes) since midnight, from 0(:00) to 23(:59). This system is used by the international time measurement standard ISO 8601. 24-hour clocks are mainly used in non-English-speaking countries in Europe, Latin America, Asia, and Africa.

In many countries, 12-hour clocks or a mixture of 24-hour and 12-hour time systems are used. Professionals in some fields prefer to use the 24-hour clock, regardless of which method is officially used in their country.

In American English, "military time" refers to the 24-hour clock system. In the U.S., it is customary to indicate the time of day almost exclusively using the 12-hour system. But the 24-hour clock is widely used in some specialized fields. These fields are military, aviation, navigation, meteorology, astronomy, computer science, logistics, and hospitals. The ambiguity of the 12-hour system when it is necessary to clarify whether an event occurred, for example, at 6 before or after noon, could lead to errors and misunderstandings.