For time adverbs, are particles instead of commas used in official (legal) writing?

Question

Even though yesterday is not an adverb, we say:

I played golf yesterday.

only because the preposition, on, is dropped before yesterday. In that on yesterday becomes a prepositional phrase that modifies played:

I played golf (on) yesterday.

That preposition dropping is a rule. What about Japanese sentences like:

昨日、ゴルフやった。

Grammatically, is there really a particle after 昨日 such as:

昨日 (では) ゴルフやった。
昨日 (に) ゴルフやった。

In speaking, you pause instead of saying the particle, but in official writing, are those possible particles after 昨日 written (instead of a comma)?

Of course, this is not limited to just 昨日 such as:

毎日、日本語を練習しています.
先週月曜日、出張した。
など...

In English legal contracts, every last preposition and comma are triple checked because they can make such a huge difference in any sort of dispute.

Now, Japanese commas seem to be void of specificity and thus open to "interpretation" by the counterparties / judge / arbiter, right? With big $ on the line, the counterparties must specify exactly what they are agreeing to, and you can't do that with commas???

Answer 1

No, you won't see any case particle after following words, official or not, as long as they're used to indicate the time when the sentence takes place on/in, because they are completely adverbial in this usage.

• 昨日, 今日, 明日 etc.
• 先週, 今週, 来週 etc.
• 先月, 今月, 来月 etc.
• 前期, 今期, 来期 etc.
• 去年, 今年, 来年 etc.
• 今朝, 明朝, 昨晩, 今晩, 今夜 etc.
• 毎日, 毎週, 毎月, 毎年 etc.

6時に荷物が届きそうだ。
夕方（に）荷物が届きそうだ。
今晩（× に）荷物が届きそうだ。
今日（× に）荷物が届きそうだ。
今週（× に）荷物が届きそうだ。

Of course, if you use those words in other ways, you must put right particles.

今日で仕事が終わる。 (by today)
今日にも荷物が届きそうだ。 (any day now)
今日（も／は）荷物が届きそうだ。 (particles other than case aren't affected)