Get the date interval from table rows, based on a start stop column
It's actually very simple. Start from the wanted date and descend the dates until you find the first row. If it's 'start' then you are inside an interval. If it's 'stop', you are not:

select 
  ( select startstop
    from mytable 
    where mydate = '2017-02-07' and startstop = 'start'
       or mydate &lt; '2017-02-07'
    order by mydate desc
    limit 1
  ) = 'start'
  as result ;


The complicated WHERE is for dealing with the inclusive date ranges. If inclusive-exclusive were used, the condition would be simper.

A similar way - perhaps a bit more clear - would be:

with ct as 
  ( select mydate, startstop
    from mytable 
    where mydate &lt;= '2017-02-07'
    order by mydate desc
    limit 1
  )
select 
       ('start') = (select startstop from ct) 
    or ('2017-02-07', 'stop') = (table ct) 
  as result ;