This calculator can be used to "add" or "subtract" two time values. Input fields can be left blank, which will be taken as 0 by default.
Add or Subtract Time from a Date
Use this calculator to add or subtract time (days, hours, minutes, seconds) from a starting time and date. The result will be the new time and date based on the subtracted or added period of time.
Start Time 




Similar to regular numbers, time can be added or subtracted. Yet, due to its unique nature, time calculations differ from those of decimal numbers. The table below illustrates various standard units of time.
Concepts of Time: Ancient Greece
In the realm of time perception, various concepts have been proposed by philosophers and scientists throughout history. Aristotle, the ancient Greek philosopher (384322 BC), defined time as "a number of movement in respect of the before and after." His perspective regarded time as a measurement of change dependent on motion or change.
Newton & Leibniz
Sir Isaac Newton introduced the concept of absolute time in his "Philosophiæ Naturalis Principia Mathematica," while Gottfried Leibniz argued that time is meaningful only in the presence of interacting objects. Newton's view held that time flows independently and is mathematically measurable. Conversely, Leibniz's relational time sees it as a concept for comparing and sequencing events. The debate between their perspectives led to significant discussions like the "bucket argument," shaping the understanding of time for centuries.
Einstein's Relativity Revolution
Albert Einstein emerged as the key figure in reshaping our understanding of time and space. Unlike Newton, who treated time as universal, Einstein's theory of relativity introduced a paradigm shift. Building on Leibniz's concept of relative time, Einstein connected space and time into spacetime, proposing that the speed of light remains constant for all observers, regardless of their motion.
Time Dilation and Spacetime
Einstein's groundbreaking ideas included time dilation, where faster motion through space leads to slower passage of time. Objects moving at nearlight speeds experience time differently, a concept demonstrated by the "twin paradox." Einstein's general relativity provided an explanation for Newton's bucket argument, connecting motion to spacetime curvature.
Unresolved Mysteries
Despite these breakthroughs, time remains enigmatic. Einstein's theories have transformed our understanding, yet the mysteries persist. Quantum physics and scientific advances continue to push boundaries, hinting at possibilities beyond Einstein's constants. As science evolves, humanity's quest to grasp the nature of time endures, perhaps leading to even more remarkable discoveries.
How We Measure Time
The Dual Forms of Time Measurement Today, when we think about measuring time, two major instruments come to mind: the calendar and the clock.
Foundations: The Sexagesimal Numeral System The bedrock of our time measurements, whether hours on a clock or days in a calendar, is the sexagesimal numeral system. This intriguing system has 60 as its base.
Historical Roots of the Sexagesimal System Journeying back in time, this numeral system has its origins in ancient Sumer around the 3rd millennium BC. The influential Babylonians then took it up, ensuring its longevity and widespread use.
Modern Adaptations While ancient in origin, the sexagesimal system has shown its adaptability. Today, we utilize it not only for time but also for measuring angles and determining geographic coordinates.
Why Base 60? But why is 60 so special? The magic lies in its status as a superior highly composite number. In layman's terms, it has 12 factors. This means that 60 is a natural number that, compared to others of its kind, boasts more divisors.
The Mathematical Magic of 60 This particular trait of the number 60 offers a myriad of benefits. For instance, it simplifies numerous fractions within the sexagesimal numbers. This innate mathematical strength is a key reason for its enduring relevance. Take an hour, for example; it's 60 minutes. These 60 minutes can be evenly broken down into various fractions  30, 20, 15, 12, 10, 6, 5, 4, 3, 2, and 1 minute. Such flexibility underpins the rationale for the sexagesimal system's pivotal role in time measurement.
With this deep dive into the intricacies of time measurement, it becomes evident that our modern systems are firmly rooted in ancient wisdom, seamlessly merging the past with the present.
Tracing the Origins of Time: Seconds, Minutes, and the 24Hour Day
The Pioneering Egyptians: Sundials and Star Patterns Long before digital watches and atomic clocks, the Egyptians turned their eyes to the sky to understand and divide time. They are often hailed as the first to split the day into smaller portions, with sundials bearing testament to this ingenuity. Interestingly, these ancient sundials split the daylight period into 12 segments. Nighttime, without the sun's guidance, presented a challenge. But the astute Egyptian astronomers discerned patterns in stars. By tracking 12 specific stars, they were able to delineate 12 divisions for the night, laying the groundwork for the concept of a 24hour day. But, nature isn't as precise as modern clocks; Egyptian divisions varied with seasons, giving summer hours more stretch than their winter counterparts.
Hipparchus and the Equinoctial Hours Fast forward to 147 to 127 BC, Greek astronomer Hipparchus introduced a transformative idea. Instead of relying on nature's uneven division, he proposed splitting the day into 12 hours of daylight and 12 of night, but he took the equinox  a day when day and night are of equal length  as his reference. These 24 hours, termed as equinoctial hours, provided a balanced approach. However, the universally recognized fixedhour days took their sweet time to become popular, only emerging around the 14th century, courtesy of mechanical clocks.
Degrees, Minutes, and Seconds: Beyond Time to Geography Hipparchus wasn’t done with his groundbreaking contributions. He conceptualized a system of longitude lines enveloping 360 degrees. Later, Claudius Ptolemy expanded on this, introducing 360 degrees for both latitude and longitude. This grid system got even more intricate as each degree was dissected into 60 parts, and then further divided into another 60. This meticulous breakdown gave birth to what we now recognize as minutes and seconds.
The Evolution of Calendars: From Julian to Gregorian Time wasn't the only concept humanity was eager to categorize. Calendars cropped up in various civilizations, offering systems to mark days, months, and years. But the Gregorian calendar stands out in its ubiquity. Launched by Pope Gregory XIII in 1582, this calendar is a refinement of the Julian calendar, conceived by none other than Julius Caesar in 45 BC. Although revolutionary, the Julian calendar drifted from astronomical events by around 11 minutes yearly. The Gregorian calendar adeptly addressed this, aligning more closely with celestial events.
In essence, our understanding of time  seconds, minutes, hours, and days  is a tapestry of insights from civilizations past, blended with technological advancements. It's a journey from star patterns in the Egyptian night sky to the ticktock of a clock on a wall, highlighting humanity's timeless quest to quantify the passage of time.
Journey Through Time: The Evolution of Timekeeping Devices
Primitive Time Indicators: Candles and Lamps Before the ticks and tocks of the modern age, early civilizations found unique ways to monitor the passing of time. Using what was readily available, cultures employed devices like oil lamps and candle clocks. Instead of ticking off exact hours and minutes, these tools were more about marking time between events – say, from one prayer to the next or from one phase of work to another.
Water Clocks: The Ancient Precision Tool Dubbed the clepsydra, the water clock stands as a testament to ancient innovation. Its mechanism was deceptively simple, relying on the steady flow of water either into or out of a container. By measuring this water, people could gauge the passage of time. With their remarkable accuracy, clepsydras became the timekeeping standard of their era.
Hourglasses: Time Through Grains of Sand Making their debut in the 14th century, hourglasses or sandglasses, became the next progression in timekeeping. Initially, they were seen in the same light as their predecessors, the oil lamps and candle clocks. However, as timekeeping became more refined, hourglasses were calibrated to represent precise lengths of time, becoming symbols of fleeting moments and urgency.
Pendulum Clocks: The Leap to Mechanical Precision In 1656, a significant evolution in timekeeping emerged. Christiaan Huygens introduced the world to the first pendulum mechanical clock. This was groundbreaking because it was the first device to be regulated by a mechanism that had a "natural" oscillation period. Huygens' invention was incredibly accurate for its time, boasting errors of fewer than 10 seconds a day.
Atomic Clocks: The Pinnacle of Precision Fastforwarding to contemporary times, atomic clocks represent the zenith of accuracy in timekeeping. Utilizing an electronic oscillator, these clocks track time based on the atomic resonance of cesium. While there are various types of atomic clocks, cesium variants stand out in their precision. So much so that the second, our fundamental unit of time in the International System of Units (SI), is determined by observing the radiation periods of a cesium atom.
In summary, humanity's quest to capture time has been an epic journey. From simple oil lamps that merely marked intervals to atomic clocks that define the very essence of a second, we've come a long way in our endeavor to quantify the intangible.
How to Calculate Time and a Half?
Calculate the timeandahalf rate by multiplying the regular hourly rate by 1.5. Then, determine the overtime wages owed by multiplying the timeandahalf rate by the total number of overtime hours worked by the employee
How to Calculate Time in Excel?
To calculate time in Excel, use the TIME function to enter hours, minutes, and seconds. Perform calculations by subtracting or adding time values using simple arithmetic operations.