A Bit Overwhelmed.

I guess you are taking the approach of defining the schedule and letting that determine
how much time you have in each place....

Slovenia is a lovely place, but would you consider going to Budapest instead of Ljubljana?
I think it would simplify the transportation considerations.

Also, you may want to consider buses as a travel option, especially for any shorter segments
of travel. Trains in Slovenia don't have as much coverage as in other countries, for instance.

While I have no firsthand knowledge, I am guessing that the overnight sleeper train experience
will be best done on the Austrian rail system.

Go back through the country-specific sub-forums on the site along with any tour books to look
for attractions you would want to visit. But, you can easily spend 3 nights in Vienna, Prague,
and Budapest without running out of things to see. Ljubljana is a bit smaller and perhaps not
enough there for 4 days.

Hello She's with Hanyak, you can do all of your rail planning on the website bahn.com (the German railway website). It has timetables for the whole of Europe. I have never done it but I believe if you call them by phone you can also book travel in countries outside Germany. It was some time ago that I heard about this possibility (on a forum such as this) so I don't know if this is current advice. The optimum time for tickets for price and selection is three months out.

I would also encourage you to visit the website The Man in Seat 61 (www.seat61.com). He gives advice for train newbies for railways across Europe.

Lavandula

3 nights each in Austria -> Slovenia -> Czech Republic

With 3 nights each I would focus on just Vienna and Prague in Austria and the Czech Republic, respectively. There is more than enough to do in those cities without travelling to other places. Lots of posts in the Austria and Czech Forums with ideas on what to do. Also, info on what is open and closed due to the holidays. I have not been to Slovenia and have no perspective.

do a sleeper train at least once

Probably not going to happen with your planned itinerary. There is no direct night train from Ljubljana to Prague. You would have to connect, which kind of defeats the whole purpose of a night train. Vienna to Prague is only about 4 hours, so no direct night trains, but lots of direct daytime trains.

For train info and resources https://www.seat61.com/index.html

One reason people get overwhelmed by train travel is that they overthink things. Train travel in Europe is not like in the US. Europe does not have Amtrak. What we have is a patchwork of commuter rail systems that touch at the edges. And the system is there for the locals, who use it to go about their every day business. So going to the station, buying a ticket, and riding a train is still pretty common.

So do not bother buying tickets for local trips in advance.

For longer trips it is a good idea to buy in advance. Not to "secure a seat" (tickets do not guarantee a seat anyway) but to take advantage of advance purchase discounts. Seat reservations are a good idea on long trips, but are purchased separately.

For international trips you can usually buy your ticket from the national railway at either end. I tend towards buying it from the railway where the trip starts.

We also have used Trainline https://www.thetrainline.com for booking between countries. The search allows you to see different train and bus companies so you can compare on one site. Then you can buy on Trainline or go to the specific train/bus line. Often there is no price difference between Trainline and the actual train/bus company you are traveling on, although sometimes there is a small difference.
The trainline app is also helpful for mobile tickets, as are the apps for the country specific trains.

Be sure to take into consideration the Christmas and New Year's holidays, and how they may affect your plans (e.g. train schedules, open restaurants, possibly closed sights on 12/24 and 12/25, plus 1/1).

Vienna...Kunsthistorische Museum, the Opera house, Schonbrunn and Hofburg Palaces, cafes for coffee and pastries, the Lippizaner horses, big new Year's celebrations with thousands flocking to the city....lots to see and do.
Prague...the astronomical clock, the Charles Bridge, Prague Castle, lots and lots of options for musical concerts, the synagogues and cemetery in the old Jewish quarter, the Spanish synagogue, the Mucha Museum...lots to see and do here also.
I haven't been to Slovenia or Hungary, but if I were to add another stop it would be Hungary, specifically Budapest. It's a natural combination with Vienna. From what I read here, there would be more difficulty with transportation in Slovenia, esp. in the winter.

Have a great trip!

The Trainline App is my favorite for booking train tickets in Europe. Very easy to use, and it’s worth the few extra cents they charge for the convenience.

Years and years ago, before there was a Trainline (or other Apps, for that matter), we took a train from Austria to the Czech Republic. At the border, the fast, smooth Austrian engine uncoupled from the passenger cars, and a slow, rough Czech engine hooked up to take it from there. I imagine the Czech rail system has improved considerably in the last 28 years.

On your way from Austria to Prague, stop in Cesky Krumlov, and spend the night. Or, at least see the castle there, before heading onward to Prague.

I may have missed something here, but you mentioned that it would be a two week trip, but you've only listed nine days in three cities. Where are you planning to spend the other five days? Are you planning to stay in one city in each country and then day trip from there?

Where are you travelling from, and is this your first trip to Europe? What sights are you planning to see in each city? Some sights will be on reduced hours, so you'll need to do some research on that.

That's not the best time of year to travel as you'll need to pack extra cold weather gear and some tourist facilities will be closed for the Christmas holidays.

You can research rail trips in many countries in Europe on this website - https://int.bahn.de/en . However that site doesn't sell tickets for all countries.

You can probably buy most of your tickets at Trainline - https://www.thetrainline.com/trains/europe . You'll have to establish an account first, along with payment information. I believe they apply a service charge now, but I've never found that to be a problem. I've always found their customer service good, however I noticed lately that some of the reviews on their CS are not always positive.

Have you travelled by train in Europe before? You may find this helpful - https://www.ricksteves.com/travel-tips/transportation/trains . This website is also a valuable source of information - https://www.seat61.com/ .

Good luck with your planning!

A few thoughts from me:

-I was going to recommend the Man in Seat 61 but see many already have! He is a great source of train info for trains worldwide.
-If you are arriving on the 24th and leaving on the 4th, that's 11 nights, so two more than you have here so far.
-My first reaction to seeing your itinerary was that a lot will be closed xmas eve/xmas/and perhaps even Boxing Day- I would check this first in the city you plan to arrive into.
-Slovenia is a beautiful place, and for me, the best things to do there are outdoors. It can be a bit grim in the winter and it's likely to be rainy when you are planning to go. If it were me, I would probably split your time between Vienna, Budapest, and Prague. Many years ago, as part of a longer trip, I did two nights in Prague, overnight train to Budapest, two nights Budapest, and then two nights Vienna. You could do the same trip in reverse and extend the number of days in each place. All three of those cities have lots to do that's indoors (plus xmas markets, which should still be up through New Year's Day) so the weather is less of an issue.

Good luck with your planning!

Sorry you are having trouble. Booking train tickets is no where as straight forward and booking a flight. It can be a challenge; especially in the context of that big holiday in coordination with transatlantic flights.

So, you didn’t give a lot of detail of where you wanted to go so I just threw somethng together using your arrival and departure dates and the locations you mentioned. The beauty is that its all with OBB the Austrian train company. I picked the dates almost at random so you can change those to your liking. Do note that you will be in Vienna over Christmas when a lot is closed so plan that carefully. I still think it can be made to work and be a nice few days. Pick where you want NYE too. I think you have two choices.

If it were me, I would skip Ljubljana. Using your air tickets another nice holiday, and one with a lot less travel time and more time to see things would be: Vienna > train > Budapest > discount airline > Prague. The markets in Budapest (and I think Vienna) stay open until 1 January so you would get to see a tiny bit of the Christmas markets.

But here is what you asked for:

24 December: Land Vienna
27 December: Vienna to Graz OBB RJ554 from 9:24 - 12:20 starts at 9.90€
29 December: Graz to Ljubljana OBB EC71 from 10:28 – 13:53 starts at 12.90€
1 January: Salzburg to Prague OBB IC641 & EC334 10:11 starts at 41.60€
4 January depart Prague

https://shop.oebbtickets.at/en/ticket

It isn't hard if you know where to look. As already suggested the Man in Seat 61 is a great starting point for train information.

I would say, however, your bones are not what I would recommend. Arriving in Austria on Dec. 24 is a worst case scenario as pretty much everything is closed on the 24, 25 and 26. You need to do a lot of advance planning to ensure you eat food. Check all museum and holiday market schedules (note that all but just a handful of markets close on Dec. 24).

As for Slovenia, where do you mean? Ljubljana? The best way to get there is by bus from Vienna as the trains are infrequent. I travel by Flixbus. If you want to explore Slovenia beyond Ljubljana, then you will need a car.

Overnight train - not really feasible on the route you are planning.

I suggest Austria and Czechia only with the time you have.

I try to answer the question before I throw in my two cents.

Now that I did that, here is what I would do, and I think it works pretty well. A bit fast, but you acknowledge that in your post and are good with it. With good planning and some flexibility you can have as good a time on a short trip as someone who stays a long time and planned nothing.

24 December: Land Vienna. Town closes up by 2pm is my guess (just a guess).

25 December: Not much open in Vienna. Ask Emily because I know here the markets open back up at about noon on the 25th. Maybe Vienna too?

26 December: I think some of the markets stay open until 1 January, but ask Emily.

Here in Budapest the Opera House has something every day of the holidays and the bathhouses are open and many of the restaurants and a few of the coffee shops. The real dead day is the afternoon of the 24th and the morning of the 25th. But Vienna is apparently different so talk to Emily.

27 December: One full day of everything open in Vienna. I think you will enjoy it.

28 December: Another full day of everything open in Vienna. Or go on to Budapest. Check both and choose which interests you more. You can't do wrong either way.

29 December: Morning train to Budapest (if you didn’t go yesterday). RJX269 from 9:40 to 12:35 starting at 17€ on the MAV rail site. Why? Well, it’s different, it’s beautiful this time of year and our markets are still open. https://jegy.mav.hu/jegy/ (Hotel Medosz or Hotel Oktogon or UpHotel or Three Corners Avenue Hotel, or K+K, depending on your style and budget).

30 December: Budapest

31 December: Budapest

1 January: Flight to Prague. 12:45 – 14:00 starting at 105€ on Ryanair. Some have heartburn over a flight. But the airports at both ends are easy to navigate and close to the towns and the flight is fast and cheap.

2 January: Prague

3 January: Prague

4 January: Fly Home.

EDIT: I will suggest that you move quickly. As hotels are getting expensive. Here, hotels that usually run under 200 a night are over 300 for the dates I put above. From that list of mine, I think the K+K will be the cheapest at about 250 a night.

And I would post in the Slovenia Forum the question, "What do I do in Slovenia between 29 Decmeber and 1 January?

I loved Slovenia but train travel is not very easy or efficient.
But the bus system is excellent, I had no problem going anywhere I wanted to go.
It's a small country so bus trips are not lengthy or uncomfortable.

Use the Trainline app as suggested above or the Omio app. They are super easy to use for booking across countries. I prefer Omio because it also includes buses. Sometimes buses may be more convenient. These apps charge a small fee but they will simplify your life.

Just be aware that neither Trainlinr nor Omio represents all of the train companies in Europe and as a result there are circumstances where you end up paying more than you need to; and there are circumstance where you are left to believe there is no train when there are trains.

Mr. E's itinerary above of Vienna/Budapest/Prague is a good one and allows for decent transportation options. All his caveats are good as well as the caveats from others about closures for the holidays and about travel in Slovenia. IMO, in winter I would prefer not to be planning bus trips just in case there are problems with weather and snow. (I have no experience in Slovenia, so I could be talking out of my hat.)

I looked at OMIO. I did this blurry eyed on a phone. So feel free to check me.

Budapest to Vienna
30 Oct only OBB tickets
31 only Regiojet tickets
1 Nov only 1 Regiojet, the rest OBB and no trains after 12:30pm
2 Nov some of each but I don't think all the Regiojet tickets were shown.

No MAV tickets on any of the dates and they are generally half the OBB cost this close to the date.

October, Mr E? Thought it is December

I just checked how accurate it was for this week. It was bad enough where I would want to check it against the national rail sites no matter when you book. If you are having to do that, why not just book with the national sites?

I suppose a few national sites are so impossible to use that this might be better but you still need to confirm everything.

Which companies dont they work with? Well, they dont tell you, so you have to confirm everything. The Trainline isnt any better on that count.

I guess there are times they have advantages .... as a last resort. For the OPs trip, tge way I played it out its OBB all the way. Easy. Good site if not a tad expensive.