* Basic metric units of length is metre, weight is gram and capacity (volume) is litre.
* Different unit measurements should be converted into same unit for addition and subtraction of units.
* a.m (antemeridien) denotes the time that is after 12:00 midnight and before 12:00 noon.
* p.m (postmeridien) denotes the time that is after 12:00 noon and before 12:00 midnight.
* To convert 12 hour time to 24 hour time, add 12 to any hours 1 p.m to 11 p.m and change 12 a.m as 00:00 hours
* To convert given time greater than 12 in railway time to an ordinary time, subtract 12 from it.
* Ordinary and Railway time are the same in a.m and it is less than 12.
* In both the formats there is no change in minutes.
* A year which is divisible by 4 is considered as a leap year.
* A century year which is divisible by 400 is a leap year.