With this release jenkins changed the build identifier to the build number (instead of timestamp). Now the BUILD_NUMBER and BUILD_ID both return the build number and there is no way to get the timestamp from the environment variables.
According to the documentation BUILD_ID should return the timestamp.
The current build id, such as "2005-08-22_23-59-59" (YYYY-MM-DD_hh-mm-ss)
- Change BUILD_ID to return the timestamp
- Add Env-Var BUILD_TIMESTAMP or similar