action.list.php can calculate $start_ts and $end_ts incorrectly for week 53.
Without an exception cooked into the if statement for case 'week': starting on
line 99, the strtotime functions on line 124 and 125 can produce the incorrect
timestamp when any days from week 53 fall into the newest year.

I write this report on Jan 2, 2021. On line 124, $start_ts get calculated with
the values 2021, 53, 1 and on line 125, $end_ts get calculated with values 2021,
53, 7. After each go through the formatting string (from line 120), they end up
as follows:

2021-W53-1 (timestamp 1641189600)
     &
2021-W53-7 (timestamp 1641794399)

Naturally, both times stamps are one year too far ahead. It appears this will
only happen when a new year starts in week 53.