If someone abandons their possessions, when does it become legal for the items to belong to the person who is holding the items?

Probably a year or two, I suspect. I would send a letter first, telling him/her that if he/she does not pick up the belongings within the next 30 days, you will sell them for storage. Send the letter by first class AND by certified, and of course, keep a copy.

No special time. enough so it appears clear that the stuff is "abandoned"don't let your live in emotions color and make you do foolish things.

Thank you for your question, it is well that you should ask. There is no exact number of days. If he does not seek the return of his property after a "reasonable" period of time, he has abandoned them. If you have any means of contacting this person, do so and advise him that if he does not make arrangements to retrieve his property within a reasonable time, you will consider it abandoned and will dispose of it. I'd say, give him 30 days, and give him reminders every 10 days and one last chance 3 days before the end of the 30 days. If he makes any reasonable requests, such as packing stuff up or allowing FedEx to come and pick it up, you should accomodate, though you are not obligated to spend any money. Keep records of all contact.