can someone create a git repository with past date
Solution 1:
It's not possible to change commit's date. But it is possible to amend commit and alter it's date.
Saying that there are two dates, commit date and author date. To change commit date set GIT_COMMITTER_DATE. Then use git commit --amend --no-edit.
To change author date, use git commit --amend --no-edit --date="new date"