Tardiness/lack of understanding of time is actually a huge problem in our culture . Most of us take it by default that other person would be at least an hour late. So we usually give an hour earlier than intended time when hosting a party or something. (We usually give actual time to our Western friends).
However, this creates problem for people who actually show up on the given time. Now you have guests in the house to entertain while at the same time make preparations for the party. It also embarrassing for guest to arrive on time only to find out that they are early.
Sometimes when we really want to convey be timeliness, we say something like 5PM American Time not Desi Time. But I really wish we don't have to do this.
We use "5PM sharp" or its equivalent in Urdu or Hindi but usually it doesn't mean much.
When we want people to be on time and don't want to assume that they will be late, we usually say a little more or give a reason (like we made reservations etc).
However, this creates problem for people who actually show up on the given time. Now you have guests in the house to entertain while at the same time make preparations for the party. It also embarrassing for guest to arrive on time only to find out that they are early.
Sometimes when we really want to convey be timeliness, we say something like 5PM American Time not Desi Time. But I really wish we don't have to do this.