Smunday is the the day between Sunday and Monday. It's the time where half the world is starting work on a Monday and the rest of the world is still clinging onto the last glorious hours of the weekend. While I'm ready to start work (I'm currently in Canberra, Australia), 90% of my twitter stream are still very obviously in "weekend" mode.
Website traffic dies down during this period as well. It won't come back up until Tuesday (Australian Time) or late Monday (U.S time).
Even the financial markets, which are open in Tokyo and Sydney, seem to be subdued. And when London comes online a few hours later, even the brits seem to be holding back until everybody is back at work.
Therefore - Nothing seems to happen on Smunday.