Units of time
In a nutshell
The units used on a daily basis are the second, minute and hour. In order to consider time frames greater than this, use days, weeks, months and years.
Hours, minutes and seconds
Unit
 Conversion
 Example

Hours  $1$ hour = $60$ minutes
 School lessons typically last an hour 
Minutes  $1$ minute = $60$ seconds
 Brushing your teeth should take two minutes 
Seconds    A heartbeat lasts a second 
Example 1
How many seconds are in $2$ hours and $3$ minutes?
$2 \text{ hours}$ = $2 \times 60$ = $120 \text{ minutes}$
$120+3 = 123 \text{ minutes}$
$123 \times 60 = \underline{7380 \text{ seconds}}$
Days, weeks, months and years
Days and weeks are constant units of time. Use the following equations to convert between units:
$1$ day = $24$ hours
$1$ week = $7$ days
Unlike days and weeks, months and years can vary in how long they are:
Months
 Duration (days)

January, March, May, July, August, October, December  $31$

April, June, September, November  $30$

February*  $28$

*On leap years, February has $29$ days instead. This means that leap years last $366$ days, while nonleap years last $365$ days.
Example 2
How many days are between March $18^{th}$ and September $2^{nd}$?
Calculate how many days are left in March:
$3118=13$
Calculate how many days make up the months between March and September:
$30 + 31 + 30 + 31 + 31 = 153$
Add the previous two values to the number of days in September:
$13 + 153 + 1 = \underline{167 \text{ days}}$
Note: As the question asked 'between', you do not need to include September $2^{nd}.$