Verified answer

it means "as I was about to go out..."

details:

verb ’よう' form + と した時 に means "as I was about to ~".

more generally, you can use verb 'よう' + と する to mean "about to~" or "attempt to~". But とした時 is quite common.

とした doesnt have an exact translation into english, a loose translation would be 'as to say'.

出かけようと思った時に means 'as i was thinking of going out', which means you happened to be making a decision when the phone rang which is pretty unlikely haha.

出かけようとした時に is 'just when i was about to go out', which sounds alot more natural (and likely).

Dekakeyou = to depart

Toshita= to try to (used after volitional verbs)

It's saying, "Let's try to go out"

No, don't say dekakeyou to omotta, it's not the same thing.

出かけようとした時に，電話があったんです

→　When I was about to go out, I had a phone call.

be about to ～ ： ～をしようとする

He is about to eat it. ＝　彼はそれを食べようとしている。

I was about to cross the street. ＝ 通りを渡ろうとした。

よう or おう make the verb a volitional form.

ru-verb should be replaced the last ru with you.

着る（kiru） → 着よう（kiyou）

見る（miru） → 見よう（miyou）

起きる（okiru） → 起きよう（okiyou）

降りる（oriru） → 降りよう（oriyou）

u-verb should replaced the last u with ou.

examples;

話す（hanasu） → 話そう（hanasou）

聞く（kuku） → 聞こう（kikou）

待つ（matu） → 待とうmatou

飲む（nomu） → 飲もう（nomou）