select SUM(T.Time-cast('0:00' as time)) FROM TABLE T 

 --Количество дней
 
select cast(cast((cast('01.01.100' as timestamp
                  )
                  +sum(cast('01.01.100 '||a.c_timeinterval as timestamp
                           )
                      -cast('01.01.100' as timestamp
                           )
                      )
                  -cast('01.01.100' as Timestamp
                  )
                 )as integer
            )as char( 3 ))
       ||' days '||
 --и время без миллисекунд
 
       extract(hour from cast('0:00' as time)+SUM(c_timeinterval-cast('0:00' as time)))
       ||':'||
       extract(minute from cast('0:00' as time)+SUM(c_timeinterval-cast('0:00' as time)))
       ||':'||
       cast(extract(second from cast('0:00' as time)+SUM(c_timeinterval -cast('0:00' as time))) AS INTEGER) c1 from t1