When you get an error stating - Work log across multiple days is not allowed.
Please follow the below steps to fix this case.
A) ID - 15344 Unable to add or update worklog
1. Go to Admin -> Timesheet settings.
2. Enable Allow multi-day work log addition and save the configuration.
Now you can add / update worklogs.
This
should be enabled when different technicians working from different
timezones (or different value is set under personalize option). The
reason is Indian timezone 12 AM is not equal to Australia timezone 12
AM, hence we should enable this option to add/update worklogs.