Are these sentences below interchangeable?
- This is a good day.
- It is a good day.
- Today is a good day.
- It is a good day today.
As far as I can remember all of them can be used.
If we can use them all interchangeably, can I also replace "day" with "week", "month" and "year" in all those sentences? Like "This is a good year.", "It is a good year.". "This year is a good year.", "It is a good year this year." etc.