Server side grouping makes sense, but the documentation for the Time axis type:
Looks like we could group? The documentation actually says:
dateFormat: 'M d',
fromDate: new Date('1/1/11'),
toDate: new Date('1/7/11')
"use this axis for listing dates that you will want to group or dynamically change".
Of course this is Charts 1 documentation, but you would think 2 should do everything 1 did and then some (hopefully faster/better).
Also, the groupBy config option here isn't explained at all in the documentation (I couldn't find it in either the charts 1 docs, or the sencha 2 docs). Neither is aggregateOp.