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Default Behavior

By default, when you drag a task bar on the Gantt chart, the start and end dates snap to the nearest scale marks. The rounding unit depends on your current time scale:
ScaleRounding Unit
Day (D, DD)Full days
Week (W)Full weeks
Month (M)Full months
Year (Y)Full years
For example, if you set the scale to Month, dragging a task rounds its start date and duration to full months. This behavior simplifies scheduling at coarse granularity but prevents precise date placement when needed.

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Disable Date Rounding

To disable rounding, add the following line to Widget Properties > Advanced > Gantt Config Script: 
gantt.config.round_dnd_dates = false;
After this change, dragging task bars places them at the exact position where you drop them, without snapping to scale boundaries.
If you are using hour-precision scheduling with the scale set to hours (H), disabling date rounding lets you position tasks at specific times within the day rather than snapping to whole-hour boundaries.

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When to Keep Rounding Enabled

Date rounding is useful in scenarios where approximate scheduling is sufficient:
  • Long-term portfolio planning at the month or year scale, where exact days do not matter
  • Sprint planning at the week scale, where tasks should align to sprint boundaries
  • Release planning where milestones align to month boundaries
The round_dnd_dates setting controls rounding for both drag (move) and resize operations. Setting it to false disables rounding for all drag-and-drop interactions.

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Verification

You should now see:
  • Task bars placed at the exact drop position when dragged, without snapping to scale boundaries
  • Dates in the lightbox reflecting the precise position where the task was dropped
  • Resized task bars ending at the exact cursor position rather than the nearest scale mark

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See Also

KB ArticlesSupport TicketsSource Code
  • prod-gantt-src/com.nextedy.polarion.gantt.client/src/js/dateConflictResolver.js
  • prod-gantt-src/com.nextedy.polarion.gantt.client/src/js/utils.js
  • prod-gantt-src/com.nextedy.polarion.gantt/src/com/nextedy/polarion/gantt/model/Config.java
  • prod-gantt-src/com.nextedy.polarion.gantt.client/src/js/lib/lightbox/util.js
  • prod-gantt-src/com.nextedy.polarion.gantt.client/src/js/main.js