Time:

A measured or measurable period during which an action, process or condition exists or continues known as time.

There are two clock hour systems

• \( 12 \)-hour clock

  • AM is the time period between midnight \( (12am) \) and noon \( (12pm) \)

  • Between noon \( (12pm) \) and midnight is PM \( (12am) \)

• \( 24 \)-hour clock

  • \( 1 \) PM is \( 13:00 \), \( 4 \)PM is \( 16:00 \), \( 11 \)PM is \( 23:00 \)

To read time, we may use both analogue and digital clocks.

Analogue clock

• It works in \( 12 \)-hour system

• It goes round once for am and once for pm

• A new day begins at midnight \( (12:00 am) \)

• Each number on the minute hand is worth five minutes.

• Individual minute indications can be seen on some clocks.

e.g.

Digital clock

• It can operate in either \( 24 \)-hour or \( 12 \)-hour mode.

• It has four digits, two for the hour and two for the minutes.

• A “:” is frequently used between the hours and minutes.

• It is not necessary to specify am or pm with a \( 24 \)-hour time.

1.11.1.1 Working with time

Time does not operate like the rest of the number system (based on tens, hundredths, and so on),

Computations can be difficult.

There are:

• \( 60\) seconds in a minute

• \( 60 \) minutes in an hour

• \( 24 \) hours in a day

• \( 7 \) days in a week

• \( 365 \) days in a year

• \( 366 \) days in a leap year

You should be aware of the number of days in each calendar month.

The following rhyme will help you to remember.

Calculation in \( 12 \)-hour system

Work in increments of time

• Calculate the minutes till the following hour, then the complete hours, and finally the minutes until the end time.

Worked example:

How long are the hours and minutes between \( 04:30 \) pm and \( 11:45 \) pm.

Work in increments of time

\( 4:30 →5:00 (30 mins) \)

Add complete hours

\( 5:00→11:00 (6 hours) \)

Remaining minutes

\( 11:00→11:45 (45 mins) \)

\( 30 \ mins+6 \ hours+45 \ mins = 7 hours \ 15 minutes \)

So, there are \( 7 \) hours and \( 15 \) minutes in between \( 4:30 \) pm and \( 11:45 \) pm

Tip:

You can solve such questions with the help of a calculator

Calculation in \( 24 \)-hour system

Work in time chunks, exactly as the \( 12 \)-hour clock computations.

• Calculate the minutes till the following hour, then the complete hours, and finally the minutes until the end time.

Worked example:

How long in hours and minutes are there between \( 07:23 \) and \( 18:43 \)

Calculate the minutes until the next hour

\( 07:23→08:00 (37 \ mins) \)

Add whole hours

\( 08:00→18:00 (10 \ hours) \)

Proceed with remaining minutes

\( 18:00→18:43 (43 \ minutes) \)

\( 37 \ mins \ +10 \ hours \ +43 \ minutes \ =11 \ hours 20 \ minutes\)

So, there are \( 11 \ hours \) and \( 20 \ minutes \) in between \( 07:23 \) and \( 18:43 \)

Tip:

You can solve such questions with the help of a calculator

Test yourself

Question 1:

When the local time in Athens is \( 09:00 \), the local time in Berlin is \( 08:00 \).

A plane leaves Athens at \( 13:15 \). It arrives in Berlin at \( 15:05 \) local time.

Find the flight time from Athens to Berlin.

Give your answer in hours and minutes.

[1]

Question 2:

Here is part of a train timetable for a journey from London to Marseille.

All times given are in local time.

The local time in Marseille is \( 1 \) hour ahead of the local time in london.

Work out the total journey time from London to Marseille.

Give your answer in hours and minutes.

[1]