Working with custom fields
Custom fields are identified by either name or id (e.g., customfield_12345). Referencing a custom field by its name is often easier to know what the value is referring to. But referencing custom fields by their id will allow the configuration to survive the renaming of a custom field.
Configured date format
For date substitution variables, the format of the replacement variable can be specified if the default format is not desirable. The format is specified by a Simple Date Format string enclosed in parentheses following the substitution variable name. For example: %created(yyyy-MM-dd)% will result in replacement like 2013-05-28.