Three dates mark the start of autumn: which one counts?

Dozens gathered in a druid grove in County Kilkenny in August to mark Lúghnasadh, the beginning of the Celtic autumn.

For many people, the season arrives with falling leaves and shorter days later in the year.

However, according to the ancient Celtic calendar, autumn has already begun since 1 August.

A different group follows the astronomical calendar, stating that autumn does not officially start until 23 September.

The meteorological calendar offers yet another date, placing the beginning of autumn on 1 September.

This system is managed by a multi-agency body responsible for planning emergency responses to major weather events.

Each calendar divides the year into four seasons but begins at different points in the year.

Confusion remains regarding which date officially marks the start of autumn in 2026.

The choice of date depends entirely on which calendar an individual or organisation follows.

It is what experts refer to as a sidereal year when discussing astronomical measurements.

For most people, the modern tradition involves falling leaves and shorter days later in the year.

By Naomi Holland for BBC News Northern Ireland.