Fillup creates intervals on holidays if the holidays fall on a weekend

[smithfarm]

Take the following hypothetical schedule:

FRI 08:00-12:00, 12:30-16:30
SAT 08:00-12:00, 12:30-16:30
SUN 08:00-12:00, 12:30-16:30

and do a fillup over the tsrange [ 1960-12-22 00:00, 1960-12-26 24:00 ) i.e. Thu-Mon, where Sat, Sun, and Mon are holidays.

The result is mystifying: intervals are successfully created on all three days according to the schedule.

[smithfarm]

And the culprit is . . . holidays_in_daterange()!

[Sun Jan 24 21:09:38 2016] DEBUG: fillup_tempintvls(): holidays_in_daterange says $VAR1 = {
          '1960-12-26' => ''
        };