There is a big problem with saving day and saving character's location in-game. When you follow the steps bellow you can duplicate all stuff that you want.(example: deerclops eyeball, guardian horn, renewable stuff, and rare stuff, ...). This bug is still working in public server (I did in Klei's server). When I did the step 6, my game's crashed. I tried to join back that server and I was in cave with my stuff (deerclop's eyeball). After that I join back surface, my stuff(deerclop's eyeball) that I stored in chest (from step 4) still there. thats meant: Deerclop's eyeball has been duplicated. Deerclop's eyeball just for example, I can do with any items that I want. I hope Klei will fix this bug.
Thanks in advance for your reply!
Step 1: Choose any item for duplicating then join cave with those items.(better join at dusk-time)
Step 2: Wait for the day to pass.
Step 3: Come back to the surface.
Step 4: Store/ drop item that you want to duplicate then wait for the day to pass again.
Step 5: Die any way you want.
Step 6: Rollback the server and enter cave when the time is counting 5...(Your game maybe crashed or loading forever)
Step 7: Join back that server. --You should be in cave at this step--
Step 8: Come back surface and you will see the items thats duplicated. You can see both in inventory and where you stored/droped at step 4.