Units of Time

Units of Time

• Units of time are standards used to measure intervals or durations
• The International System of Units (SI unit) of time is the second
• Other commonly used units of time are minutes, hours, days, weeks, and months

Brief Examples of Time Measurement

• Blinking: a few seconds
• Brushing teeth: a few minutes
• Flight from Canada to Paris: a few hours
• Symptoms of the flu: a few days
• Significant growth of a sapling: a few weeks
• Pregnancy: many months

History of Time Measurement Units

• Time measurement study is called horology
• Measuring of time started over 30,000 years ago
• Early societies used astronomical objects like the moon, sun, and stars to determine time
• Sundials and moon patterns were used to estimate time
• Later, standard units and clocks were developed to measure time
• Today, time is measured based on the vibrations of the cesium-133 atom

Types of Time Measurement Units

• Second: base unit of time, used for very small intervals (blinking, breathing, snapping)
• Minute: larger than a second, smaller than an hour, used for small intervals (drinking coffee, taking a walk, boiling water)
• Hour: largest unit of time, used for large intervals (baking a cake, studying)
• Day: made up of 24 hours, used for intervals like waiting to hear back from an interview
• Week: made up of 7 days, used for intervals like using products within a week
• Month: made up of 30 or 31 days, used for intervals like salaries being credited
• Year: made up of 365 days, used for intervals like birthdays

Converting Units of Time

• To convert units, multiply or divide by a conversion factor
• Examples of conversions:
  • 1 minute = 60 seconds
  • 1 hour = 60 minutes
  • 1 hour = 3600 seconds
• Conversion steps:
  1. Recall the relation between the units
  2. Smaller to larger unit, divide
  3. Larger to smaller unit, multiply
  4. Write the correct unit in the answer

Examples of Converting Units of Time

• Convert 720 seconds to minutes: 720 / 60 = 12 minutes
• Convert 18 minutes to seconds: 18 x 60 = 1080 seconds
• Convert 185 minutes to hours and minutes: 185 / 60 = 3 hours 3 minutes
• Convert 20 days to hours: 20 x 24 = 480 hours
• Convert 7893 seconds to hours, minutes, and seconds: 7893 / 3600 = 2 hours 11 minutes 33 seconds