Which file contains the date of the last change of a user's password?

/etc/gshadow stores encrypted group password information and secure group attributes, not user password change dates.

/etc/passwd contains basic user account information like username, UID, GID, home directory, and shell, but not the password hash or last change date for security reasons.

/etc/pwdlog is not a standard file for storing password change dates on Linux systems.

The /etc/shadow file stores secure user account information, including the encrypted password, password expiration policy, and the date (in days since epoch) of the last password change.

/var/log/shadow is not a standard file; /etc/shadow is the correct path for password hashes and associated dates.