How to determine Sabbath day in the Jewish calendar?

Question

I'm trying hard to understand it by reading the internet, but still I fail to elaborate what is in my mind as I am still unable to understand it.

First, I would like to propose the things I know about International Calendar.

1. The name of the month change after date 29 or date 30 or date 31.
2. So, the date it self is "reset" to 1 at each time the month name change.
3. But the name of the day (Monday to Sunday) is still continue (no reset).

From the point above, when I heard "the first day of the month", then this means :
-. date 1
-. Whatever the name of the day on date 1. Means, the name of the first day of the week is not fixed.

From the internet, I found this link say :

What’s interesting is besides Sabbath — which is the name of the seventh day of the week — there are no names for the days of the week in the Jewish calendar. The days of the week are known as the first day, second day, the third day, and so forth

So, since there are no names for the days of the week, but the seventh day (the Sabbath )... I wonder how to determine that "today is Sabbath", as I read in the OT verse something like this :
The fourteenth day of the first month (Numbers 28:16)
The fourteenth day of the second month (Numbers 9:11)

What I thought at the beginning :
A. That "fourteenth day" in the verse is Sabbath, the second Sabbath of the month.

then my following logic :
B. Each of the new month, the day is "reset" to 1,
so the first day of the month = the first day of the week.

Continue the article in the link:
Nisan: It contains 30 days
Iyar : has 29 days

So, assume that today is Nissan 28, the Sabbath (the fourth Sabbath of Nissan) - then :
Tomorrow is the 29th day of Nissan, the first day of the week.
The day after tomorrow is the 30th day of Nissan, the second day of the week.

The continuing logic is :
On the first day of Iyar, it is the third day of the week.
This means what I thought before in point-A (consequently my conclusion in point-B) is wrong.
The "fourteenth day of Nissan" is not a certainty that it is the Sabbath...
it maybe fall on the Sabbath but maybe not.

Last conclusion for the time being :
The day of the month is resetting to 1 at each new month, but the day of the week is not resetting to 1 ... it still continue if it's not the seventh day of the week.

But then, from Wiki - it say :

14 Nisan – Fast of the Firstborn – on 12 Nisan when the 14th falls on Sabbath

While other article say that the Sabbath is fixed on each N(th) day of the month. In this case the 8th, 15th, 22nd and 29th :

Leviticus 23:39 the Father commanded us to start the Feast of Tabernacles on the 15th day of the 7th month, which is a sabbath, making it a High Sabbath. Then on the eight day of the Feast, on the 22nd, He said it is also a Sabbath, proving the pattern of 8th, 15th, 22nd and 29th.

That other article above almost the same thing on what I thought in point-A and B :
Each new month, the day is "reset" which is called the first day.
(mine is one day earlier, though).

So, my confusion :
How to know that today is the Sabbath ?
Is it based on the day of the month ? resetting the day of the week is involved
Or is it based on the day of the week ? the day of the week continue if it's not the 7th day of the week

Any kind of respond would be greatly appreciated.
Thank you in advanced.

Answer 1

In Genesis, the seventh day of creation was the first Sabbath. Ever since then, every seventh day has been a Sabbath.

Answer 2

UPDATE

In the article What Is The True Sabbath Day?, you are citing an article that misunderstands the Sadducee error on the counting of the omer between Pesach and Shavuos. The Sadducees make the mistake of thinking that the count of the omer must start on the Sunday following the first day of Passover (the 15th of Nisan) rather than the day after Passover (the 16th of Nisan) as we did from the beginning. The article compounds this error by pretending that not only does this mean that the 16th of Nisan must occur on Sunday every year, but that this error is extended to every month. This of course is total garbage and has never been part of any calendar, not even that used by any sectarian during the past.

One of the obvious errors is a misquote from the mythology of John that in that year the Passover was on the Sabbath and pretends that it is saying that every year has the first day of Passover occurring on the Sabbath.

---

ORIGINAL

You have misunderstood the calendar. The days of the week are based on the days of creation. Thus the first day of the week is counted from then with the seventh day on which Hashem rested we have the seventh day. Each week continues from that point every seven days. The month on the other hand is based on the cycles of the moon. At each new moon the day of the month is counted as one no matter what day of the week it may occur. The cycle of the moon is approximately 29.5 days. Thus each new month would start one or two days later in the week. Av is 30 days. For example The first of Av this year (5780) was Wednesday July 22. The first of Elul will be Friday August 21.

Since most years are not evenly divisable by 7, the new year would be be on a different day of the week each year.