Description:
When create user-defined date field format DD MMMM YYYY, NNN and insert in document works properly but when file is saved and exited then re-opened the format is lost and date code is shown. Opening field format the format is there under User-defined and can be inserted into document.

Steps to Reproduce:
1. Open file
2. Delete date code
3. Ctrl-F2
4. Re-select user-defined date format
5. Insert
6. Save and exit file
7. Open file and date code is shown not user-defined date format

Actual Results:
When document opened date field shows date code

Expected Results:
When document opened date field should an DD MMMM YYYY, NNN


Reproducible: Always


User Profile Reset: Yes



Additional Info:
Version: 6.4.4.2 (x64)
Build ID: 3d775be2011f3886db32dfd395a6a6d1ca2630ff
CPU threads: 8; OS: Windows 10.0 Build 18363; UI render: GL; VCL: win; 
Locale: en-US (en_US); UI-Language: en-US
Calc: CL