Why で in 今日で最後にしたいです?

Question

Referring to the clock that counts the time since the last nuclear test:

時計の数字を変えるのは、今日で最後にしたいです。
I want to make today the last day where I change the figure on the clock.

I'm confused by the particle で in this sentence. Maybe I've mistranslated, but I would have expected it to be 今日を. I'm thinking of the pattern AをBと/にする meaning "make A as/into B".

Depending on the explanation there's also a possibility I'll be confused as to why it's で and not に, but at the moment I don't see how either one works.

Answer 1

Both 今日を最後にしたいです and 今日で最後にしたいです are perfectly fine. In the latter case, で is a particle used to mark a time limit, deadline, finish time, etc. 明鏡国語辞典 says:

⑤㋑区切りをつける点。期限。限度。「三日で仕上げる」「この作業で終わりだ」「明日でお別れだ」

So you can think で is used with verbs related to finishing, ending, exiting, quitting, etc.

• この学校を来月で卒業します。
  ＝ この学校を来月に卒業します。
  (×この学校に来月で入学します is wrong)
• この仕事は昨日で終わりました。
  ＝ この仕事は昨日終わりました。
  (×この仕事は昨日で始めました is wrong)
• このイベントは来年度で終了します。
  (×このイベントは来年度で開始します is wrong)
• タバコは今日でやめます。

Answer 2

As you can see from Jisho.org here, で can be used when:

1. indicates location of action.

2. indicates time of action​.

3. indicates means of action; cause of effect.

I'm pretty sure the second one is the one being used here.