Hello, I bought an e-ticket online through the Russian Railway official site, to go from St. Petersburg to Moscow, and just discovered I bought it for the wrong day. I'm pretty sure the ticket is refundable, although I don't see how to do that online.
Has anyone had experience with this? I'm wondering if I will be able to exchange my ticket for the correct day, or if I should buy a new ticket (before they sell out) and then figure out how to return the one I have.

Thanks for any advice

Does this page from the website help? If not, use the contacts page on the website to get in touch with someone who can help you.

E-tickets refunds using the site | Passengers

Thank you, Odin. I've read and re-read that page, and I don't think it explains a way to get a refund online. I think I may have to return it at the train station in St. Petersburg when I get there.
I have written to the contacts listed, asking if I can exchange dates, but it's Sunday in Russia and I imagine I wouldn't hear back until Monday at the earliest. Meanwhile, there are only a few
spaces available on the train I want to take, so I think I had better buy a new ticket and hope to return the ticket I have.

I think you are right:

If you have used the electronic registration service, returning of unused e-tickets on train:

• on domestic routes on the territory of the Russian Federation and international services to/from CIS countries, the Republic of Estonia, the Republic of Latvia, the Republic of Lithuania and the Republic of Abkhazia made no later than 1 hour before the train's departure from the train's starting station (time is specified in the control coupon of the electronic ticket);

Hopefully you have purchased a refundable ticket.

I think unfortunately I have purchased a non-refundable ticket. Is that what "Full" means? I bought a 1st class sleeping compartment ticket on the overnight Krasnya train. There is a statement about sleeping compartment tickets being non-refundable. However, there is also a statement about refunding a non-refundable ticket, so I am quite confused. I think I will wait on buying a new ticket, and hope to hear from the ticket office. I had planned to go on a Sapsan train leaving St. Petersburg at
11 am; then I decided to go the night before, arriving Moscow early morning, to have several more hours in Moscow. I mistakenly bought a ticket for the following night. If I can't resolve my mistake, I could buy a second ticket--or I could spend the extra day in St. Petersburg, use the ticket I have, and have 3 days in Moscow instead of
3 1/2 days.

Maybe you can rebook your ticket once you are in St Petersburg, if you go to Moscovsky station and ask them to rebook, which I know might be too late as those trains are popular. My interpretation, which might be wrong, is that non refundable tickets are FULL, they are rebookable subject to availability & fees but not refundable if you cancel. But hopefully you can get a reply from them to clarify. Pity to lose time in Moscow.

I think you may be right about rebookable vs refundable, and what I want to do is rebook. I got a preliminary response to my email to the ticket office, saying it will take time to answer me. I'll wait a bit and see if I hear from them. Thanks again.