Maybe this is true in some places, but not in Colorado, nor in most other US states AFAIK. See for instance law.justia.com/codes/colorado/2022/title-31/article-2/part-2‌​/…: "If a majority of the registered electors voting thereon vote for a proposed amendment, the amendment shall be deemed approved."

Approved means the majority voted for it, in this instance, not approved as in a law was made right then. @NateEldredge

In this case it does create the law all by itself, I'm quite sure of it. I'll look for more citations.

It clearly does not. There are many ballot measures that never become law. Those that do are rewritten and passed.

Can you give a specific example in Colorado?

Of a ballot measure not becoming a law?

Yes, of a ballot measure that was approved by voters but did not become law due to inaction by the legislature. (Not counting instances where it was struck down by a court, or repealed later, etc.)

Pick any of them. You can look up the actual law then and see it is written differently.

In all the ones I've checked, the text of the statute is identical. So let's take for example Colorado Proposition 121 of 2022, which lowered income tax rates. It's now part of Colorado Revised Statues 39-22-104, section 1.7. The footnote shows it as enacted by the proposition itself, not by any act of the legislature. If you believe that an act of the legislature was needed to enact it into law, can you point me to the corresponding session law?

What are the dates each one was passed?

Prop 121 passed in the general election of November 8, 2022. If the legislature did act on it, they would have had to do so very fast, because the new rates were printed on the tax forms for tax year 2022, which appeared in early 2023. But politically, I don't think this proposition was favored by the legislature at the time, and I'd be surprised if they took any affirmative action to pass it.

What date was the law passed?

What I'm suggesting is that there was no separate law passed by the legislature, because I believe that the passage of the ballot proposition amended the statute law all by itself. I'm challenging you to find such a legislative act if it exists. I don't think that it does.

If you think it does it, and it does, it would be written as such. The date the law was changed will match if you are right.

The CRS page I linked above, in footnote 11, shows Section 1.7 as having been amended by Proposition 121 which passed on November 8, 2022. It does not reference any other legislative act nor any other date. If the legislature had acted to enact this amendment, surely we would expect to find a corresponding footnote in the Revised Statutes?

And the History section at the end of the page shows only Prop 121 as amending Section 1.7, effective upon proclamation of the Governor on December 27, 2022, whereas all other amendments show a House Bill or Senate Bill number.

What is the date of the passage of the law?

We seem to be going around in circles. I don't know what you mean when you say "the passage of the law". I presume you mean some action of the legislature, and I'm asserting that there is none, so there is no such date.

It can not amend a law and the law has no date that it was passed.

According to the history at the same page I linked, section 39-22-104 was repealed and re-enacted in its entirety, effective June 22, 1987. Section 1.7 was added effective August 2, 2000; amended June 6, 2005; amended again by Proposition 116 effective December 21, 2020. But I don't see how those are relevant to the question at hand.

The dates would have to be the same as when it was voted on, for the ballot measure to make a law.

Okay. I'm going to try one more time, and then go to bed. Section 1.7 today has a tax rate of "four and forty one-hundredths percent". Prior to 2022, it didn't. How did that text get there? The only relevant footnote shown is for Prop 121, passed by voters on Nov 8, 2022, and proclaimed by the Governor on December 27, 2022 (a purely ceremonial and non-discretionary function that simply announces the election results), and suggests that it was effective immediately upon proclamation (i.e. on 12/27/2022). [...]

If you think that the proposition alone did not actually insert that text into the law, and that it was some other legislative action that did so, then I ask you to find it. I believe that all the information you would need should be on the CRS page for 39-22-104, linked in an earlier comment. I can't provide any further information because I don't think it exists.

The law was never changed on the day of the vote.

That's true, it was changed on the date of the governor's proclamation of the election result. But that's not a legislative function. It adopted the exact text approved by the voters, and my understanding is that nobody would have had the authority to draft other text.