We have new charts from our chart guy, boviscopophobic
I'll use data from this January since CIG has graciously refrained from having major sales events that corrupt the statistics.
These are the raw* hourly incomes over the past week. You can see that there are peak hours straddling the midnight GMT boundary, but there is noise that obscures the pattern a bit. You can also see that random $10000+ spike which is not, despite what one might think, actually a Wing Commander pack (unless store credit was used) and a probable War Pack ($5000).
These are the smoothed high-res income data over the same week. It's a bit easier to see the 24-hour cycle here since the noise is smoothed out.
Finally, this is the average income per hour for the first four weeks of January. The big peak is 20-21 GMT, but I'd say 20-0 or 1 GMT are usually pretty busy hours. It's not really clear what that means; it could indicate Germans who are arriving home from work, Californians on lunch break, East Coasters buying ships at work, people on disability with erratic sleep schedules, ...
*) The hourly incomes are actually interpolated from time points that aren't sampled exactly on the hourly boundaries.