One-way sync end date field is visible only when:
- End date field is synchronized with: Original Estimate
- End date field is synchronized with: Time Spent + Remaining Estimate
One-way sync start date field is visible only when:
- Start date field is synchronized with: Original Estimate
To see a one-way sync field change the start/end date field mapping to a time tracking field and save the changes. A corresponding one-way sync field will appear. 
One-way sync of Start/End date
The Start/End date can be mapped and uni-directionally synchronized with an additional Jira field.
This is a one-way sync from the App to Jira.
This one-way sync. From BigPicture/BigGantt to Jira does not disrupt the functioning of Start/End date fields. First, you set up the standard field mapping for the Start/End date - based on that, the field value of the Start/End date field is established. Then, the App takes the Start/End date value and updates a selected Jira field with it.
For example:
- The End date is based on Time Spent + Remaining Estimate.
- The App uses the End date value to visualize tasks on the timeline.
- The End date field value is used to update the value of the Due date Jira field.
Synchronization is uni-directional, so changing the Due date in Jira won't alter the end date in the App.
The additional mapping follows the same rules as normal mapping - i.e., you cannot select the same field to be both the End Date and the additional End Date.
Only simple Date and Time fields can be selected for additional mapping (fields such as Time spent and Remaining estimate are not available in the drop-down).