Google's server-side java library requires that all DateValue objects
added to a table be expressed in GMT. However, the rendered JSON sent
to the client contains no timezone information, and the client-side
response.getDataTable() call constructs new javascript Date objects
using the local timezone.
A simple fix would be to have the JSON renderer generate a Date
constructor that uses milliseconds past epoch instead of
year,month,day,hour,minute,second. Not only would doing so resolve
timezone discrepancies, but it would also significantly reduce the
amount of text marshaled and de-marshaled.
For example, in
com.google.visualization.datasource.render.JsonRenderer.appendCellJson(),
use
case DATETIME:
calendar = ((DateTimeValue) value).getCalendar();
valueJson.append("new Date(");
valueJson.append(calendar.getTimeInMillis());
valueJson.append(")");
break;
instead of
case DATETIME:
calendar = ((DateTimeValue) value).getCalendar();
valueJson.append("new Date(");
valueJson.append(calendar.get(GregorianCalendar.YEAR)).append(",");
valueJson.append(calendar.get(GregorianCalendar.MONTH)).append(",");
valueJson.append(calendar.get(GregorianCalendar.DAY_OF_MONTH));
valueJson.append(",");
valueJson.append(calendar.get(GregorianCalendar.HOUR_OF_DAY));
valueJson.append(",");
valueJson.append(calendar.get(GregorianCalendar.MINUTE)).append(",");
valueJson.append(calendar.get(GregorianCalendar.SECOND));
valueJson.append(")");
break;
Chris
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