# Time

60 seconds = 1 minute
60 minutes = 1 hour
24 hours = 1 day
7 days = 1 week
52 weeks = 1 year

365 days = normal year
366 days = leap year

Leap years are divisible by 4
Centuries are not leap years unless divisible by 400

## Calendar

January   31 days
February   28 days (29 in leap year)
March     31 days
April        30 days
May     31 days
June           30 days
July         31 days
August     31 days
September  30 days
October   31 days
November  30 days
December  31 days

## 12 hour and 24 hour clock

12 hour clock times are written with
am to represent morning
and pm to represent afternoon.
A colon is used to separate minutes.

Examples
9 :30 am  is half past nine in the morning.
9: 37 pm  is 23 minutes to ten in the evening.

24 hour clock times are written with 2 digits to show hours
and a colon to separate minutes.

Examples
09 :30  is half past nine in the morning.
21: 37  is 23 minutes to ten in the evening.

Military usage of 24 hour clock times
drops the  colon
and adds the word hrs.

Examples
09 30 hrs  is half past nine in the morning.
21 37 hrs  is 23 minutes to ten in the evening.

## Converting between 12 hour and 24 hour clock times

To convert from 12 hour clock times to 24 hour clock times,

• drop the am or pm
• add 12 to the hours if the time is in the afternoon ( pm)

Examples
9:30  am    =  09:30   or   09 30 hrs
3.15 pm   = 15:15    or  15 15 hrs

## To convert from 24 hour clock times to 12 hour clock times,

• subtract 12 from the hours if  the 24 hour time is between 13:00 and 24:00    or    13 00 hrs and 24 00 hrs
• drop the  hrs if it was there
• add am if the 24 hour time is is between 00:00 and 11:59
• add pm if the 24 hour time is is between 12:01 and 24:00

Examples
03:15  = 3:15  am
23:23   = 11:23 pm
11 27 hrs = 11:27 am
21 00 hrs = 9 pm

## Conversion table

 Time 12 hour 24 hour Military Midnight = 00:00 00 00 hrs 1 am 2 am 3 am 4 am 5 am 6 am 7 am 8 am 9 am 10 am 11 am Midday 1 pm 2 pm 3 pm 4 pm 5 pm 6 pm 7 pm 8 pm 9 pm 10 pm 11 pm 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 01 00 hrs 02 00hrs 03 00 hrs 04 00 hrs 05 00 hrs 06 00 hrs 07 00 hrs 08 00 hrs 09 00 hrs 10 00 hrs 11 00 hrs 12 00 hrs 13 00 hrs 14 00 hrs 15 00 hrs 16 00 hrs 17 00 hrs 18 00 hrs 19 00 hrs 20 00 hrs 21 00 hrs 22 00 hrs 23 00 hrs Midnight 00:00 00 00 hrs

## Calculations with time

Do not use your calculator – unless you are using the Deg,Hour,Min function.
Otherwise, your answer will not be converted properly.

Examples

calculate the time difference between
a) 11:07 and 11:30        b) 11:07 and 12:00

examples
calculate the time difference between :-

a) 11:07  and 11:30

b) 11:07 and 12:00

C) 09:45 and 17:38

Remember

4.1 hrs = 4 hours 6 minutes , not 4 hours 10 minutes.

 Hours Minutes 1 60 0.05 3 0.1 6 0.15 9 0.2 12 0.25 15 0.3 18 0.35 21 0.4 24 0.45 27 0.5 30 0.55 33 0.6 36 0.65 39 0.7 42 0.75 45 0.8 48 0.85 51 0.9 54 0.95 57

## World Time

World Time calculator

Time zone codes

Why change Time ?