Rail travel Zurich to Geneva

There is a European wide schedule change due about Dec 9. Otherwise the Swiss only sell tickets inside of 30 days. They also have a system generally referred to as: "Buy a ticket and get on the train." They will not sell out, and their website www.sbb.ch/en will show the expected degree of crowding on any given train, very light, moderate, or crowded. There is a direct train every 30 minutes. You could also look at a Supersaver ticket, inside 30 days for up to 50% off, but you must ride the train on the ticket.

Kate T, I used trainline.eu to see if tickets are available for you and got as far as putting my name in but stopped there. I believe you'd be able to buy it through trainline now. I prefer using trainline because it's so convenient. They'll also notify you if there's an upcoming strike.

I'd be surprised if trainline will sell you tickets that are not for sale by the operator. Like I say, SBB does not sell tickets until 30 days before the scheduled departure. BTW, looking at trains for Monday, Nov 13, the only train that is expected to run with a lot of people in 2nd class is the 8:32 departure. The 9:03 is wide open.
Other then Supersaver tickets, Prices are always the same and good on any train that day. Most Swiss just buy their tickets right before traveling out of a vending machine, or increasingly, with an app on their smartphone.

Kate, why do you want to buy this ticket in advance? There are some supersaver tickets, but the system is designed to be "turn up and go".
Just go to the station, buy a ticket from the machine (which will be valid on any train that day), and get on the next train - easy.

Look up times on https://www.sbb.ch/en/
There are two trains per hour, leaving at 03 and 32 minutes past the hour, taking ~2h45.

Italy, France - buy THOSE tix ahead of time. Switzerland - just buy them at the station or from your sbb app. No need to buy Swiss tix ahead of time.

Kate, you're a first time rail traveler. Rail travel is not like airlines where there are a limited number of seats which get booked up long in advance. Its more like the subway, or buses. Local people use them for everyday travel and commuting, so they don't necessarily plan and book months ahead. In many European countries, there are big discounts for buying in advance, but not Switzerland. Long distance and international trains would be different.

Thank you all so much for your information and advice!! I was only concerned at a busy time of year and we are flying from Singapore so after a long flight, I didn't want to risk not getting train tickets on the day of arrival. Thank you.

Kate, Intercity trains from Zürich to Geneva look like this: https://upload.wikimedia.org/wikipedia/commons/0/00/IC2000_Z%C3%BCrich_-_Luzern.jpg
Each train has 1000 seats and they run every 30 minutes. That is an awful lot of capacity!
There is no seat reservation. As Stan said, it is just like a métro (I think its called MRT in Singapore), everybody just turns up at the station and gets on the next train. Tickets are valid on any train.

My son-in-law is Swiss and lives in Geneva. He laughed when I asked him about reservations on Swiss Trains. The only time I've ever had reserved seats in Switzerland is when I arranged for school group travel. In that case SBB reserves a whole section of the train just for my group.