All PC’s and networking devices use clocks to maintain an internal system time. These clocks, called Real Time Clock chips (RTC) provide time and date information. The chips are battery backed so that even during power outages, they can maintain time.

Computer networks rely on timekeeping for nearly all their applications, from sending an email to saving data, a timestamp is necessary for computer to keep track. All routers and switches need to run at the same rate, out of sync devices can lead to data being lost and even entire connections.

This article explains the world’s global timescale - UTC (Coordinated Universal Time)  what it is, why it was adopted and how important it is now.

What time is it? One of the commonest questions uttered
around the World but what exactly are we asking? You ask someone in China what
the time is then you will certainly get a different answer if you ask an
American, obviously their time-zones are on the opposite side of the world. 

But what if you ask two people in the same room as you? You
may get the same answer from them both but then again one person’s watch may be
a minute or two faster.