Is "time period" a redundant expression?

While period does refer to calculated time, it also refers to more organic (temporally contiguous) divisions. We reference Picasso's 'Blue Period' as a piece of time associated with when Picasso painted blue things. The length of time associated with the Victorian Period is usually stated as 1837-1901, but this is only one of many attributes of the Victorian Period/Era.

So while you're correct in theory, in practice, we use 'time period' as referring to the numerically quantifiable length of time. This sets it apart from a period's other attributes.

Technically, you are correct. However, the phrase is idiomatic. It sounds better than your second example, while in your third example the "periods" might be misconstrued as a reference to a hockey game.