I called them for you as well,
It is as you said, they are closed until 20th of April - and they opened only exceptionally during Christmass and sometime during February, but was not sure what occassion was this.
Hope you can enjoy better meal there around as well, enjoy your holidays
P.s. If you call after working hours, you will get an auto message that is in both high german and french telling detailed info. and that what helped me to understand a bit better than if someone answered me