The date-time picker (expiry times, announcements, log cleanup and the
dashboard filters) and the date range filter on the log pages stopped
at the minute: editing a time reset its seconds to zero, and confirming
a range again dropped the seconds it had. Both now show and keep
seconds, and the range filter button shows them too.

Emptying the time field, for example with Backspace on one part of it,
sent out an invalid date. The field now goes back to its current time
instead.