This is something very stupid. But it just occurred to me. Suppose my clock is set to a time say 5 mins ahead of the actual IST. Now a little lag or lead is bound to occur. Similarly there may be someone else with a lag of say 5 mins. Many of us set the time after checking with our own friends, or sometimes is the aeroplane, when the pilot announces the time on landing. That may be another 5 mins lagging the already lagging time. This way, it can go on and on, and I wonder if like in one time zone itself, there are like people living with time gaps of upto 40 mins or so. Considering this above condition, I think this is quite possible. Now still, how do we check with each other. I think hence, the best way to like co-ordinate is to tell the time gap rather than the actual time. That way, people will be on time even if like their clock times differ by many mins. For example, if you want to fix a meeting or a game of football, instead of saying meet at 5:15, we should say, meet after 45 mins exactly. So we should give the relative timings rather than absolution. Actually, considering the complexity in everything now-a-days, I think relativity everywhere is quite necessary. To avoid lots of confusion.
In short, the time lags or leads which I think arre present, should not lead to problems. No matter what time zone you live in, the time you follow will be the time for you...