saving seats before activating JR pass?

We arrive on Tokyo on december 26, which is very close to the new years eve, therefore, we need to save seats on the train to Kyoto, which we are planning to take on december 30, since we realized its a very busy day in Japan because meny people are heading back home from the big cities.
things i, we only want to activate our JR pass before heading to Kyoto... But the question is, can we save seats on the train to Kyoto before activating the JR pass?

You never activate a JR Pass, I really wonder why so many people use this nonsensical term.

You can exchange your pass on the 26th, and request that its validity period start on the 30th. Then you can immediately reserve a seat for a trip on the 30th.

Firas, there's no need to be so rude. "Activate" is a common term when it comes to the JR Pass and does make sense - you are "activating" it for use.

Actually for the JRP you purchase an exchange voucher that you "exchange" for the pass. If we want to be pedantic (and Frias does).

When doing the exchange, you can specify the start date up to 30 days later (and the valid period runs 7, 14 or 21 days), and you can also reserve seats for the valid period once you have your pass, even though it may not be valid for travel until a later date.

After you get the pass, the voucher is rubbish - not worth keeping, even as a receipt because the passes are not able to be reissued.

As for "activation" while not a technical term that would normally be used, obtaining the first stamp on entry to the railway system could be considered "activation of the pass".

I don't think @Firas is trying to be rude they just raise an interesting linguistic point. Then give the correct information. I don't know why everyone says "activate" either. It may be that similar systems in their home countries talk about activating tickets. I suppose thats the way language works.