fix typo: mixed posix_time and gregorian classes when build date from string
Security Notice: GitLab has uncovered a widespread malicious npm supply-chain attack that potentially can destroy user data. All teams are required to audit packages. Further information can be found under the Computer Security Report for November 2025 and the original blog post in https://about.gitlab.com/blog/gitlab-discovers-widespread-npm-supply-chain-attack/
fix typo: mixed posix_time and gregorian classes when build date from string