Second is the smallest unit of time and 60 seconds together make one minute. Similarly next higher unit of time is hour. An hour is formed by 60 minutes.
Now we will further study about number of hours in a day. A day has 24 hours. So now lets see how to do calculations related to time:
To convert days into hours we proceed as follows:
1 day = 24 hours,
So 2 days = 2 * 24 = 48 hours,
3 days = 3 * 24 = 72 hours,
In the same way if we need to convert the hours into days we will have to divide the number of hours by 24.
So to convert 72 hours into days, we write:
72 / 24 = 2 days.
Proceeding further we see that 7 days combine together to make 1 week, so to convert days to weeks, we will simply divide the number of days by 7.
Thus we say if we need to convert 42 days to weeks we write:
42 / 7 = 6 weeks.
Proceeding to months and years, we say that different months have different days i.e. either 30 or 31 days. There exist a special month February which has 28 days each year but every 4 th year, month of February has 29 days. This year is called as leap year.
To check if the given year is a leap year or not, we will divide the year by 4. If it is completely divisible, then it is a leap year else not.
To check 2012, we divide 2012 / 4 = 503, so it is completely divisible, thus this year is a leap year.