You could add some dummy rows - with dates, but with Freq set to 0 or missing.
dt = New Table( "test",
Add Rows( 20 ),
New Column( "date",
Format( "d/m/y h:m:s", 22, 0 ),
Formula( Today() + In Days( Row() ) )
),
New Column( "freq",
Set each value(if (contains({5,6,7}, row()), . , 1) )
)
);
dt << Graph Builder(
Variables( X( :date ), Frequency( :freq ) ),
Elements( Bar( X) )
)