How to display date in email subject.

If we use default_subject then we are getting date in email subject.

My Format: Junit Test Build # 20 2012-09-12 4am

I find Below Tokens only :

${DEFAULT_SUBJECT}
${DEFAULT_CONTENT}
${PROJECT_NAME}
${BUILD_NUMBER}
${BUILD_STATUS}
${CAUSE}
${BUILD_URL}
${FAILED_TESTS}
${CHANGES}
${CHANGES_SINCE_LAST_SUCCESS}