Demetrius is one of the few people in Stardew Valley who subscribes to science rather than magic. He is a scientist living in Stardew Valley and he earns his keep by studying the surrounding wildlife, be it plants or animals. He is married to Robin the carpenter and has two children; Maru who is Robin and Demetrius’ daughter and a son named Sebastian who is Demetrius’ stepson. He is Robin’s son from her old marriage. Incidentally, Sebastian is one of the characters in Stardew Valley whom you can marry therefore Demetrius is potentially one of your fathers-in-law.
Demetrius, like many others, has a schedule which differs from season to season. To explain his schedule correctly we have to divide it by the seasons.
Spring: On Mondays, Thursdays and Sundays Demetrius stays at home. On Tuesday he stays home until 3:50 pm at which he goes to the Mountain. On Wednesday he goes to the west of the Community Center from 12:30 pm to 4:00 pm. He also stays home when it is raining.
Summer: In summer you can find him west of the Community Center from 4:00 pm to 7:00 pm on all days except Friday. On Friday he has three options. He either stays home, spends time in his laboratory or goes to the saloon and dances with Robin there. The rain rule also applies in summer as he stays home when it is raining.
Fall: During Fall he follows the same pattern as in summer but with a twist. Instead of being near the Community Center he goes to the lake which is near the mines. He goes there from 12:00 pm to 7:00 pm and at any other time you can find him in his home. On Friday he will either go to his lab or to the Saloon. He stays home if it is raining however.
Winter: Winter is probably the best time for you to catch Demetrius as he stays at home or in his laboratory.
If he is not there then he is probably standing with Robin behind the counter.
Demetrius’ Gift Guide:
There are many gifts that you can give to Demetrius that will make him really happy. Gifts that you can give which have a positive effect are Rice Pudding, Bean Hotpot, Strawberry, Ice Cream, Purple Mushroom, any Fruit and any egg except for the Void Egg.
Whatever happens you should not give Demetrius Quartz, Holly, Universal Hates or Universal Dislikes.
One of the most important events with Demetrius involves the cave in your farm. He comes to your farm and tells you that he would like to set up a study in your cave. You can choose between Mushrooms and Bats.
If you choose Mushrooms then every two days Mushrooms will spawn in your cave and you can harvest them. If you choose bats they will drop fruit which you can either sell or make in to jam and sell for an even bigger profit.
He also has two heart events at three and seven hearts and they both give you recipes.
Demetrius is an interesting individual as he is the only stepfather in Stardew Valley. He is also the only scientist and there are a bunch of interesting conversations that you can have with him. He also gives you gifts depending on how well your friendship with him is.