Wifiless, plug-in only calendar

Hi, Christmas is coming and I noticed my grandmother struggling to find the right day and forgetting what plans she has. Obviously she doesn’t have WiFi in her house. Does anyone know about a digital calendar that I can set up once and then it just keeps running reliably without WiFi? Features like adding her weekly plan would be amazing but if that’s not possible then something that simply tells her the day and is always turned on would already be amazing. Do you guys know a product like that?

I tried looking on Amazon but it’s hard to distinguish if they need WiFi or not.