There seems to be a lack of knowledge about the flexible use of the word: day.
Flexibility isn't what is needed.
Careful attention to context is.
In Scripture the word day has shades of meaning, or units of time that vary in length.
It isn't a matter of "shades".
It is a matter of context.
For example:
All of the creative days are summed up by the word 'day' at Gen. 2 v 4.
Not so. It says that all of those things just mentioned prior about the 7 days of creation pertained to generations (of people) ["these are the generations"] and that it took about 1 day unto the Lord in order to accomplish the organization of it all. This is the process of taking the genealogy of everyone who lived in a prior cycle of creation and organizing them into a new cycle of creation. This ["in the day they were created (organized)"] period of time is also the same thing as the Judgment Day being spoken of here.
The reason this took one day is because this was the period of time during Adam's life that He performed this great labor. He is who was to acquaint himself with every "creature" and to give to them their "new name". Some would be named as "fishes" (Christians) and some would be named as the next cycle's Noah, Melchizedek, Abraham, Isaac, Jacob, Joseph, Moses, Jesus, and so on. This great work would encompass nearly the entirety of Adam's life, which is about a Millennium.
A Creation is like a pageant or a production that repeats over and over again. That's why all of the holy books that pertain to it are called "scriptures". There is a script that is written that plays out each time. And, the master blueprint of that "script" is the creation account itself. Each Day is a seal that when opened up reveals the hidden will of God in relation to what has been "scripted" to take place upon that Day, which is a period of about 1,000 years. Its what says who, when and where, depending upon the name you were given by Adam, comes fourth in their "word to come". The name we receive from Adam fore-ordains us to a particular level of glory. We received a fleshly glory and some receive a heavenly glory.
The 'day' of Genesis 2 v 17 is as Peter mentions at 2nd Peter 3 v 8.
God's day is: one-thousand years in length.
Or, as the Psalmist wrote that in God's eyes or viewpoint a thousand years is as yesterday or a watch in the night. [Psalm 90 v 4]
That the 'day' of Genesis 2v17 is a thousand years is also shown in the ages of people at their death. Adam lived under 1000 years dying at age 930.
Even the oldest person in Scripture died before age 1000 dying at age 969.
Hope the ^ above ^ has been of some help.
It is a good start, but things aren't "flexible" as you put it.
You can tell when the day as 1,000 years is applicable if it pertains to the Lord's reckoning of time and not man's reckoning of time.
It should also be helpful to understand that Adam was a body of flesh and bone, not a body of flesh and blood. This means Adam was a society of individuals who are all united as members of a distinct spiritual body by way of solemn covenants to bring them all into a state of union.
Therefore, the lifespan of this society is more in keeping with 930 years versus having that be the lifespan of a person like you or I in flesh and blood to live that long. Adam is a group of individuals in union by means of a covenant who form a distinct society, which society shall undertake the labor of passing judgment upon all who have ever lived and sealing them into the new cycle of creation to follow.
Thus, keep an eye out for what society has a keen interest in genealogical info and is organizing them into a new family structure via priesthood power. That society is the Lord of Creation and your King. Unfortunately, that society is presently in a very fallen state, for the time being.