Units of Time

Units of time and the whole concept of tracking time are important to people for different reasons. A baker must know how long to keep her bread in the oven. A parent has to have a good understanding when his son is coming home from school. A doctor needs to know how long you’ve been experiencing symptoms to prescribe medicine.

Time measurements also serve as milestones. A worker may get paid every two weeks. Nearly all of us celebrate the annual milestone of being born on our birthdays. And, relationships are celebrated on anniversaries.

Time is a precious commodity. We’re all given only so much time on earth. When something has great value – as time does – there’s a need to track it by breaking the whole down into units. This page shows the common units of time that most folks learn as children.

    Units of Time

    Common Units of Time

    The big three units of time are seconds, days, and years. If you extended it to seven, it would be seconds, minutes, hours, days, weeks, months, and years.

    • 365 days make up one year.
    • One year is 52 weeks plus one day.
    • One year has 12 months.
    • One day has 24 hours.
    • One hour has 60 minutes.
    • One minute has 60 seconds.
    Common units of time

    Seconds Anyone?

    The word “seconds” comes from Latin meaning the “second small part” after minutes.

    • One billion nanoseconds make up one second.
    • One minute has 60 seconds.
    • One hour has 3,600 seconds.
    • One day has 86,400 seconds.
    • One week has 604,800 seconds.
    • One month has about 2,592,000 seconds (assumes 30-day month).
    • One year has 31,536,000 seconds.

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    All about seconds - units of time

    Every Minute Counts

    Like seconds, minutes come from Latin meaning “first small part.”

    • One hour has 60 minutes.
    • One day has 1,440 minutes.
    • One week has 10,080 minutes.
    • One month has about 43,200 minutes (assumes 30-day month).
    • One year has 525,600 minutes. (If you’ve seen the musical “Rent,” you know this one)

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    Measuring with Minutes

    Hour by Hour – Units of Time

    Hour, the 24th part of the day, is derived from Old English, French and maybe Greek.

    • One day has 24 hours.
    • One week has 168 hours.
    • One month has about 5,040 hours (assumes a 30-day month).
    • One year has 8,760 hours.
    Hour measurements

    Larger Units of Time

    Historically, units of time were based on the day, the solar year, and the phases of the moon.

    • Seven days make up one week.
    • 15 days make a fortnight.
    • 28 to 31 days make up a month.
    • Three months make a quarter (of a year).
    • Six months make up a semester of half-year.
    • 12 months make up a year.
    • Two years make a biennium.
    • 10 years make a decade.
    • 20 years make a score. (Remember the Gettysburg Address? Four score and…)
    • 100 years make a century.
    • 200 years make a bicentennial.
    • 1,000 years form a millennium.
    Larger time measurements


    Here are some frequently asked questions about units of time.

    What are the three units of time?

    Seconds, days, and years. The other units of measurement can be derived from these big three.

    When was time measurement invented?

    It is believed the ancient Egyptians began using sundials prior to 1,500 B.C. The basic unit of time during this period and for thousands of year after this was the period of daylight.

    How many days in a year?

    There are 365 days in a year.

    How many seconds in a day?

    There are 86,400 seconds in a day.

    How many seconds in a year?

    There are 31,536,000 seconds in one year.

    What is a decaminute?

    10 minutes.

    What is a kilosecond?

    1,000 seconds or 16 minutes and 40 seconds.

    What is a quadrimester?

    Four months.

    What are the units of time in Spanish?

    Second: El segundo
    Minute: El minuto
    Hour: La hora
    Day: El dia
    Week: La semana
    Month: El mes
    Year: El ano

    What is a galactic year?

    The galactic year is based on the rotation of the galaxy. It is typically measured in million years.

    What is a yottasecond?

    About 31.7 quadrillion years. Whoa! So, if you hope you don’t get the flu for a long time, you might say, “I hope my next flu comes in a yottasecond.”

    By Greg Johnson and Mike O’Halloran

    Greg and Mike are co-founders of ListCaboodle.


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