Vaadin Grid shows wrong year if date is the 31th of December

Question

I've created a vaadin grid and used the setItems method in combination with a custom jpa repository that returns a paged stream. The problem appears when the grid has to show a date with a specific date (2019-12-31), it will automatically show "31.12.2020", looks like the date is somehow jumping to the next year.

here the grid

private Grid<Budget> createGrid() {
        Grid<Budget> grid = new Grid<>(Budget.class, false);
        grid.setPageSize(100);
        grid.setSortableColumns();        
        grid.addColumn(new LocalDateRenderer<>(Budget::getValidfrom, "dd.MM.YYYY")).setHeader("Gültig von");
        grid.addColumn(new LocalDateRenderer<>(Budget::getValidto, "dd.MM.YYYY")).setHeader("Gültig bis");
        for (Grid.Column<Budget> c : grid.getColumns()) {
            c.setAutoWidth(true).setFlexGrow(2);
        }
        return grid;
}

here how I fill the grid

grid.setItems(query -> service.getLimitData(filter, query.getPage(), query.getPageSize()).stream());

dataset in database

dataset in vaadin grid

Answer 1

tl;dr

Change YYYY to uuuu to correct your formatting pattern.

Your issue has nothing to do with Vaadin specifically. Date formatting is standard Java.

Week-based year versus calendar year

Your formatting code is incorrect.

Uppercase YYYY means a week-based year, not a calendar year. That code uses the ISO 8601 definition of weeks and week-based year: Week starts on Monday, runs a full 7 days, and first week contains the first Thursday of the calendar year. That means the first and last weeks of the week-based year may have a few days from the previous/next calendar year.

So the unexpected year you encountered is a feature, not a bug.

For calendar-year, use lowercase yyyy or uuuu.

These formatting pattern codes are documented on the Javadoc for the DateTimeFormatter class.