"What time is it?"

Adapted from :http://www.coe.uh.edu/archive/science/science_lessons/scienceles3/

History

Stonehenge

Throughout history, time has been determined by using the reflection of the sun, the phases of the moon, and other calendars such as Stonehenge. Stonehenge, built over 4000 years ago in England, where used to tell ancient civilizations the time of the day and year. Ancient peoples used lunar eclipses, sun rays, the position of the sun, and other seasonal or celestial events to determine the time. People used these stones to tell the time of the day.

In 46 BC Julius Caesar decided that the calendar year should have 365 days, but every fourth year there should be an extra day, which would be a leap year. He adapted this basis because if the year was divisible by four then it was to be a leap year.

In 1582 Clauvius proposed the Gregorian Calendar to Pope Gregory with an average year of 365.2425 days and 97 leap years every 400 years. The year was not to be a leap year unless it were divisible by 100 and 400.

Today time can be easily determined by reading a clock, watch, or even easier by a digital clock. 

Units of Time

   

The common units for measuring time in the customary system are seconds, minutes, hours, days, weeks, month, and years.

 It takes about a second to say "one."

It takes about a minute to watch a TV commercial.

It takes about two hours to see a movie at a theater, or 3 to watch Titanic.

From the smallest unit of time to the largest, they appear:

Seconds Minutes Hours Days Weeks Months Years

Many foreign countries and all branches of the military services use a 24-hour clock to determine their time. Some employees may also use a 24-hour clock to record your work hours.

The 24-hour clock does not use A.M. or P.M., instead all hours are counted on a 24-hour basis from midnight to midnight. Times are shown as 4 digit numbers without using a colon. Zeros are added if necessary to make a 4 digit number.

Hours from 1 P.M. to 11:59 P.M. are found by adding the hour to 12.

12-Hour Clock

24 -Hour Clock

2:00 A.M. 0200

5:30 A.M. 0530

11:45 A.M. 1145

12:00 Noon 1200

2:00 P.M. 1400

5:30 P.M. 1730

11:45 P.M. 2345

12:00 Midnight

2400

Conversion Chart MEASURES OF TIME

1 minute (min.) = 60 second (sec.)

1 hour (hr.) =60 minutes

(min.)

1 day = 24 hours (hr.)

1 week (wk.) = 7 days

1 year (yr.) = 52 weeks (wk.)

1 year (yr.) = 12 months (mo.)

When converting any unit of measurements if you want:•To change to a larger unit, divide. •To change to a smaller unit, multiply.

Quick Practice1. The amount of time it takes to take a shower

15 minutes

15 hours

2. The time it takes to wash one load of clothes

45 minutes

45 seconds

3. The time it takes to cook a turkey

6 minutes

6 hours

4. The time it takes to build a house

18 months

18 years

5. The time it takes to change the oil in a car

20 minutes

20 days

 

Write the equivalents.13 months = _______year _____months

46 hours = ______minutes

34 minutes = _______seconds

68 weeks = _____years_____weeks

987 day =______years _____months _____weeks___days