Description:
------------
---
From manual page: https://php.net/function.strftime
---

When adding a time interval to 'last Sunday' on a Sunday, you get an incorrect timestamp when interval is longer than a week.  'last Sunday' becomes 'this Sunday'.

Test script:
---------------
/* Example code was run on Sunday Nov 17, 2019 */

var_dump(
$saturday = strtotime('last Saturday'),
(strtotime('last Saturday + 1 day') - $saturday) / 86400,
(strtotime('last Saturday + 2 day') - $saturday) / 86400,
(strtotime('last Saturday + 3 day') - $saturday) / 86400,
(strtotime('last Saturday + 4 day') - $saturday) / 86400,
(strtotime('last Saturday + 5 day') - $saturday) / 86400,
(strtotime('last Saturday + 6 day') - $saturday) / 86400,
(strtotime('last Saturday + 7 day') - $saturday) / 86400,
(strtotime('last Saturday + 8 day') - $saturday) / 86400,
(strtotime('last Saturday + 9 day') - $saturday) / 86400,
$sunday = strtotime('last Sunday'),
(strtotime('last Sunday + 1 day') - $sunday) / 86400,
(strtotime('last Sunday + 2 day') - $sunday) / 86400,
(strtotime('last Sunday + 3 day') - $sunday) / 86400,
(strtotime('last Sunday + 4 day') - $sunday) / 86400,
(strtotime('last Sunday + 5 day') - $sunday) / 86400,
(strtotime('last Sunday + 6 day') - $sunday) / 86400,
(strtotime('last Sunday + 7 day') - $sunday) / 86400,
(strtotime('last Sunday + 8 day') - $sunday) / 86400,
(strtotime('last Sunday + 9 day') - $sunday) / 86400,
$monday = strtotime('last Monday'),
(strtotime('last Monday + 1 day') - $monday) / 86400,
(strtotime('last Monday + 2 day') - $monday) / 86400,
(strtotime('last Monday + 3 day') - $monday) / 86400,
(strtotime('last Monday + 4 day') - $monday) / 86400,
(strtotime('last Monday + 5 day') - $monday) / 86400,
(strtotime('last Monday + 6 day') - $monday) / 86400,
(strtotime('last Monday + 7 day') - $monday) / 86400,
(strtotime('last Monday + 8 day') - $monday) / 86400,
(strtotime('last Monday + 9 day') - $monday) / 86400
);

Expected result:
----------------
int(1573880400)
int(1)
int(2)
int(3)
int(4)
int(5)
int(6)
int(7)
int(8)
int(9)
int(1573362000)
int(1)
int(2)
int(3)
int(4)
int(5)
int(6)
int(7)
int(8)
int(9)
int(1573448400)
int(1)
int(2)
int(3)
int(4)
int(5)
int(6)
int(7)
int(8)
int(9)

Actual result:
--------------
int(1573880400)
int(1)
int(2)
int(3)
int(4)
int(5)
int(6)
int(7)
int(8)
int(9)
int(1573362000)
int(1)
int(2)
int(3)
int(4)
int(5)
int(6)
int(14)
int(15)
int(16)
int(1573448400)
int(1)
int(2)
int(3)
int(4)
int(5)
int(6)
int(7)
int(8)
int(9)