This is the question I wrote in Japanese before.
Once again I will question in English. Excuse my poor English.

This problem comes up in "Doit.im for Windows".
I am using both Windows 7 and 10, and I found it under both circumstances.

When I drag and drop tasks, the deadlines are incorrectly shifted.
It occurs only in case of shifting from "today" to "tomorrow" by Drag&Drop.
On the other hand, the followings are all OK;
• today --> schedule (by Drag&Drop)
• tomorrow --> today (by Drag&Drop)
• tomorrow --> schedule (by Drag&Drop)
• schedule --> today (by Drag&Drop)
• schedule --> tomorrow (by Drag&Drop)
• Any group --> Other group (by editing task)
I signed out and signed in again, but this could not be solved.
Furthermore, I uninstalled the app and re-installed and yet the result is still same.

Your answer is much appreciated and I expect some improvement in the program.