You can specify custom group size and date/time format for the time header rows.
The result time header HTML can be further customized using BeforeTimeHeaderRender event.
Group Sizes (GroupBy)
Supported group sizes (and the default format string):
Hour
Default date/time format pattern: "H"
Day
Default date/time format pattern: the format string specifed using datePattern property of the current locale, "M/d/yyyy" for Locale.US
Week
Default string: ISO week number if the week starts on Monday, otherwise the US week number
Month
Default date/time format pattern: "MMMM yyyy"
Quarter
Date/time format example: "Q1"
Year
Default date/time format pattern: "yyyy"
None
A single cell, uses an empty string.
Cell
Cell size corresponds to the cell duration.
Default
Uses the value defined using CellGroupBy property. This is a legacy option.
JavaScript
Example:
dp.timeHeaders = [
{ groupBy: "Year" },
{ groupBy: "Month" },
{ groupBy: "Day" }
];