Most date surprises have one of these causes.
A bar looks one day longer than expected #
An end date without a time is inclusive: a task from Monday 5 to Friday 9 covers the whole Friday, so the bar ends at the end of that day. That matches how people read a plan. If you mean “until the start of Friday”, enter the end as Thursday, or add a time.
A duration ends later than you counted #
With weekends on (the default), a duration counts working days: 5 days from Thursday ends on the next Wednesday. Holidays are skipped too. Clear Count durations in working days under Edit > Timeline to count calendar days.
Day and month are swapped #
Dates typed as text (03/04/2026) are read with your Excel language settings, so they can mean 3 April or 4 March. Check the stored value rather than its alignment: =ISNUMBER(A2) tests whether A2 contains a numeric value such as an Excel date serial; =ISTEXT(A2) tests for text. A number still needs to represent the intended date. Convert them with Data > Text to Columns (choose Date in the last step), or type them in ISO form (2026-04-03).
Two-digit years or odd years #
Text dates with two-digit years follow Excel’s rule (00 to 29 means 2000 to 2029). Workbooks created on old Macs can use the 1904 date system; SimpleGantt detects it, but dates copied between a 1904 and a 1900 workbook move by four years in Excel itself. Check File > Options > Advanced > Use 1904 date system.
A task appears in the wrong place or not at all #
- An end before its start, an error such as #N/A, or text in a date column puts the row under Issues. Click the issue to go to the cell.
- A lighter, striped bar with dates in italics means the start or end was calculated (from predecessors or the duration) because the cell is empty.
- A dashed outline and a warning icon mean the typed date contradicts a dependency. The table wins; change the date if the dependency is right.
The time scale is not what you want #
The automatic scale (Auto on the Zoom menu) fits the plan to the frame. Choose a fixed one with Zoom on the toolbar, or click Fit to width to go back.