If you want to use a group size smaller than one hour you need to use groupBy: "Cell" which matches the grid cells.
Your screenshot shows a timeline where one cell == one day. You may need to replace this single cell (10 am - 5 pm) with multiple 15-minute cells. This will let you select these 15-minute blocks with snap-to-grid enabled (https://doc.daypilot.org/scheduler/snap-to-grid/) and it will also fix the time headers.
Let me know if it didn't help.
Comment posted by Henry 8 years ago.
Perfect, thank you for the help.
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