Why does the publish time of new problems always shift for 3 hours?

[echip]

I don't know who advised the 3-hours-shift scheme? But I don't think it is reasonable. Because the members who will compete when the new problems publish come from three main areas: Europe, East Asia(China, Japan,...,etc), and USA.

It is Pacific Ocean from East Asia to USA, there are almost no countries between. It is not countries everywhere. So I think 3-hours-shift is not necessary.

[euler]

You're assuming that the optimum time you like to solve problems is the same for everyone. Some people are early birds, others are night owls. The regular and predictable time shift presents a best opportunity for everyone.