Everyone knows the strtotime function.
With it, for example, we can retrieve the date of 2 weeks ago,
strtotime ('-2 week');
or a year ago
strtotime ('-1 year');
What is interesting is that you can retrieve the date of 2 weeks ago while defining the time, for example midnight
strtotime ('2 week midnight');
or noon:
strtotime ('-2 week noon');
the full list can be found at the following address here