### Update 21/02/2020: the 2020.02.0 update released today includes this issue among its fixes, so this workaround should not be necessary if you update to that version and then try to import the April 2020 workbook###
This is an edited version of my post from last year for the same problem. Kudos to Marc and others who have been helping with the numerous repeated questions on this matter. Hopefully posting a fresh solution will draw the attention of new users with this problem and help stem the tide.
The April 2020 workbook omits the week of April 6-12 due to this year's Memorial falling on the midweek. What this means for Theocbase is that it will only see 3 weeks instead of 4 when importing the workbook, and these weeks (April 13-19, 20-26, 27-May 3) appear a week earlier than they should.
The following steps helped me correct this:
1. Backup the Database (just in case)
2. Import the April 2020 Workbook
3. Find the Database location (in Settings), and then close Theocbase
4. Open the Database (whether with DB Browser for SQLite or whatever one you prefer) and carry out tasks a/b/c listed below (in order) in each of the 3 following tables (again in order):
1) lmm_schedule 2) lmm_schedule_assist 3) lmm_meeting
a. find all entries with the date 2020-04-20 and change these to 2020-04-27
b. find all entries with the date 2019-04-13 and change these to 2020-04-20
c. find all entries with the date 2020-04-06 and change these to 2020-04-13
5. make sure all the changes have been written (in DB Browser, select Write Changes) and then close the Database
6. Restart Theocbase
7. Enter the appropriate Exception for the week of April 6-12
Please refer to the other posts/replies by Marc and others regarding other issues connected with this problem (for e.g iOS not syncing these changes).