Using the js Date() object in a json eventsource can offer substantial performance improvements over XML eventsource or json using iso8601 strings for the dates.

{'start': new Date(1216,2,15),
'end': new Date(1216,2,18)
}

Note: using Date() objects obviates the need for an explicit 'dateTimeFormat': 'iso8601', declaration at the top of the file. so just:

{'events' : [
{'start': new Date(1211,3,12),
}
.
.
.
]}

Note especially: the js Date() object takes three arguments: Date(year,mo,day) and it uses zero-indexed months: 0 => Jan, 1 => Feb, ..., 11 => Dec

Note also the bug as of 8/7/07: to display solid bars for duration events you must use:

{'isDuration': false,
}

Or, as I just discovered: use no isDuration property at all.