I realize the errors and limitations of online trees. I never just “copy and paste” that information into my own tree. Some trees are more than riddled with errors.
But if that tree has a totally new to you date and place for an event in your ancestor’s life–an ancestor for whom you’ve never found anything regarding that event in their life. Do not just copy the information to your tree. One option would be to put the information (and source) in the notes for that ancestor. Then ask yourself “if the date and place were correct what reliable records with reliable information” could have provided that information?
A date and place of death may be mentioned in an obituary, a church record, or a death record. The date and place of death may have been suggested by a date in a probate file. The “date and place of death” may actually have been the last known date and place the person was living and their software converted “last alive date” to “death date.”
The same analysis goes for any date and location in an online tree. If it’s true (which it may not be)…where could a record actually state it or imply it? One also has to think about how much time should be spent trying to validate a date in an undocumented tree.
Some would suggest the researcher put the date/place in their database and cite the tree as their source and then analyze it. My preference is, if I am going to “use” information in undocumented online trees as all, is to put that information in my notes or “things to followup on” file—not my actual tree.