how do I check in bash whether a file was created more than x time ago?

Only for modification time

if test `find "text.txt" -mmin +120`
then
    echo old enough
fi

You can use -cmin for change or -amin for access time. As others pointed I don’t think you can track creation time.

I always liked using date -r /the/file +%s to find its age.

You can also do touch --date '2015-10-10 9:55' /tmp/file to get extremely fine-grained time on an arbitrary date/time.