Cron Scheduling for Synchronising Data from External Directories

For synchronising data from external directories you can only specify a synchronisation interval (e.g. every 12 hours) but not an exact timestamp (e.g. 6am/6pm). For large directories this sync (especially a full sync) puts heavy load on the confluence system for quite a long period of time and slows down the confluence instance significantly. I want to be in control of when this sync is happening and prevent it from falling into the main working hours. This is impossible with just the interval, as every unexpected system restart shifts the synchronisation start time.

Jira seems to already have such a feature implemented, so it can't be too difficult to move it to Confluence as well.