原因・理由N1
〜ことだし
since... / and besides... / given that...
Structure
普通形 + ことだし
Explanation
Since the first clause (a known reason), the main clause follows; a soft, tentative way of giving a reason.
Examples
みんな集まったことだし、そろそろ始めましょう。
Everyone's here, so let's get started.
もう遅いことだし、今日はこの辺で終わりにしよう。
It's already late, so let's call it a day.
Note
The main clause is often a suggestion (ましょう/しよう). Softer than から.