A calendar chart is a visualization used to show activity over the course of a long span of time, such as months or years. (see the doc of Google)
You can display one or more lines on your chart. Each row represents an X position on the chart—that is, a specific time; each line is described by a set of one to three columns.
|0||date, datetime, or timeofday||Dates|
|N||string||Optional roles - tooltip|
Each option is separated by a '|' or '!' (for Mediawiki).
||You can use the configuration options of Google. See the doc|