Requirement: Add 30 days to trandate in workflow in a custom field.
Solution:
- Generate a workflow to set the custom date field in the transaction records.
- Add Set Field Value action to set the value in custom field.
- Trigger ON: Before User Edit
- Event Type: All
- Context: All
- Select the custom field in Parameters field.
- Check Formula radio button and add the following formula to add 30 days to trandate:
nlapiDateToString(nlapiAddDays(nlapiStringToDate(nlapiGetFieldValue('trandate')),30),'date')
Workflow:

Output:
