For the duration of martial law a holiday will not be shifted to the following after, if the holiday is Saturday or Sunday. Respective provisions are prescribed in the Law of Ukraine On Labor Relations under Martial Law.
So, Pentecost on Sunday 12 June will not be shifted to a business day. Respectively, Monday 13 June 2022 is a business day, including for the banking system.
Interbank transfers in SEP will be transacted from 11 through 13 June 2022, with the banking day being 13 June 2022.
For reference: regardless of the war, SEP continues business as usual, free of disruption, like in times of peace. All Ukrainian banks are connected to SEP and are making payments to customers almost 24/7 without days-off with consideration of both bank and customer needs.