This is today,
but this is yesterday,
actually, in some way,
this is tomorrow,
from a certain perspective,
it could be yesterday,
or some other time in the past,
today is today.
This poem is about this blog post and time. It is curious when blog posts are posted, because the date a blog post is written, the date it is posted, and the date it is read, can all be different dates. So time varies. That is the idea of the poem.
The more detailed explanation of the poem below, is somewhat confusing, because it deals with ideas like today, tomorrow and yesterday, which are variable depending on perspective (today, for now, is today, but tomorrow, it will be yesterday). Hopefully it can be followed, and no mistakes were made in it.
The first line is about right now, as this is being typed (on July 20, 2015), but, this post, is for tomorrow (July 21, 2015), so, if this is posted tomorrow (July 21, 2015), then from the point of when it was posted (July 21, 2015), this is yesterday (the second line in the poem and really today (July 20, 2015)).
The next two lines in the poem [actually, in some way/this is tomorrow] reference the idea that this post is supposed to be posted tomorrow (July 21, 2015). The next three lines though, [but/from a certain perspective, it’s today] references the idea that if this is read by a reader tomorrow (July 21, 2015) then from the point of the view of the reader, it is today (July 21, 2015, which is the date the post was (will be?) posted).
But, since this post could be read some time after tomorrow, from the point of view of the reader it could be yesterday (if the post was read on July 22, 2015 and the reader saw that the post was posted on July 21, 2015), which references the lines [although/depending/it could be yesterday], or it could be seen as [some other time in the past], for example last week, if a reader were to read this post on July 28, 2015.
Despite all of the time references above though, as the poem says [but/for now/today is today], meaning, before this is posted, it still is the present.