に当（あ）たり or
に当（あ）たって is a formal grammar pattern in Japanese used to convey the meaning of 'at the time of (A)', 'when doing (A)', or 'on the occasion of (A)'. Like
に際（さい）して 'on the occasion of (A)', it will often be used in regard to preparation for future events. This structure is a combination of に, and the う-Verb 当（あ）たる 'to hit', or 'to come into contact' in either its formal-conjunctive form or て-form.
に当（あ）たり will appear following verbs in their dictionary form, or nouns. There are two primary nuances that this structure will be used for, so let's look at a few examples of each.
The first is when (A) is some sort of special occasion or condition from which (B) will be done.
就活（しゅうかつ）を始（はじ）めるに当（あ）たり、新（あたら）しいスーツを買（か）った。
On the occasion of starting my job search, I bought a new suit.
卒業（そつぎょう）にあたって、みんなで卒業（そつぎょう）旅行（りょこう）として韓国（かんこく）に行（い）った。
On the occasion of graduating, we all went to Korea as a graduation trip.
The second is when (A) is some sort of goal or target for which (B) will be the means or measures in response to that goal.
転職（てんしょく）をするに当（あ）たり、インターネットで自分（じぶん）に合（あ）った会社（かいしゃ）を探（さが）すことにした。
At the time of changing jobs, I looked for a company that will suit me well on the internet.
新（あたら）しいお店（みせ）の開店（かいてん）にあたって、オープニングスタッフを募集（ぼしゅう）しました。
We recruited opening staff at the time of opening a new restaurant.
Caution - Unlike
に際（さい）して, which can be used for either positive or negative situations,
に当（あ）たり will primarily only be used for positive or neutral situations.
母（はは）の葬式（そうしき）に際（さい）して必要（ひつよう）な書類（しょるい）を準備（じゅんび）した。
I gathered all the necessary documents at the time of my mother's funeral.
母（はは）の葬式（そうしき）に当（あ）たって必要（ひつよう）な書類（しょるい）を準備（じゅんび）した。
I gathered all the necessary documents at the time of my mother's funeral. (Unnatural Japanese)