Railways and airlines use the 24-hour clock format as they operate round the clock (24 hour). The main features of 24-hour clock system are:
1. a.m. and p.m. are not used in order to avoid confusion.
2. Time is shown by 4 digits. The first two digits indicate the number of hours, and the next two digits indicate the number of minutes.
3. Time is expressed continuously from 00.00 (midnight) to 24:00.
