How can i get the pullrequest time?

Bitbucket Development Bitbucket Data Center
1

Hi all , i use scriptrunner to connect Bitbucket,and my Bitbucket is Data center.
now i write listener code when pull request merge,
like this

PullRequestMergedEvent pullRequestMergedEvent = event
def pullRequest = pullRequestMergedEvent.getPullRequest()
for (int i = 0 ; i < pullRequest.getReviewers().size() ; i++) {
def getReviewers = pullRequest.getReviewers()
	log.warn("getReviewers=${getReviewers}")
	def getUser = pullRequest.getReviewers().getAt(i).getUser() 
	log.warn("getUser=${getUser}")
	def commitDate = pullRequest.getReviewers().getAt(i).getLastReviewedCommit()
	log.warn("commitDate=${commitDate}")
}

and i get the log

pullRequest.getReviewers().size() : 1
getReviewers=[InternalPullRequestParticipant{lastReviewedCommit=a52b5014247ae31d7b10ebc962315d630bb20dfe, role=REVIEWER, status=APPROVED, user=InternalNormalUser{id=3, username=admin}}]
getUser=InternalNormalUser{id=3, username=admin}
lastReviewedCommit=a52b5014247ae31d7b10ebc962315d630bb20dfe

and i want to know when this commit create, like(“yyyy-MM-dd’T’HH:mm:ss’Z’”)，
can somebody help me !!
thanks