Here something that might work...
-- change -18000 to the appropriate time zone
select
c.last_name, c.first_name, DateAdd(ss,(log.login_time) -18000,'19700101') as [Last Login]
from ca_contact c
join session_log log on log.contact = c.contact_uuid
where DateAdd(ss,(log.login_time) -18000,'19700101') >= '2015-06-15'
and
DateAdd(ss,(log.login_time) -18000,'19700101') <= '2016-03-31'
order by
DateAdd(ss,(log.login_time) -18000,'19700101')