on the occasion of; at the time of; when
Formal expression used to introduce the occasion or time when something happens. Often used in speeches, announcements, and formal writing. Similar to に際して and にあたって.
開会にあたり、一言ご挨拶申し上げます。
On the occasion of the opening, I would like to say a few words.
新年にあたり、皆様のご健康をお祈りいたします。
At the start of the new year, I wish you all good health.
に際して emphasizes the special or significant nature of an occasion, while にあたり is more neutral and can also apply to routine events.
に当たって has the same meaning and formality as にあたり, but にあたり is the continuative form and feels slightly more literary.
にあたり is a terser, more literary variant of にあたっては, commonly seen in written notices and reports rather than spoken language.
Derived from the continuative form of 当たる (あたる) with the particle に, literally 'in hitting/coming upon (a time/event)'. The expression became a fixed formal phrase.