Query to obtain cccurrences within a certain period of time
You need to do some grouping for it

CREATE TABLE Table1
    ([ClientId] int, [RecordDateTime] datetime)
;

INSERT INTO Table1
    ([ClientId], [RecordDateTime])
VALUES
    (1, '2019-02-14 14:05:49'),
    (1, '2019-02-14 14:06:34'),
    (1, '2019-02-14 14:07:19'),
    (1, '2019-02-14 14:08:49'),
    (1, '2019-02-14 14:09:34'),
    (1, '2019-02-14 14:10:32'),
    (1, '2019-02-14 14:12:32'),
    (1, '2019-02-14 14:14:18'),
    (1, '2019-02-14 14:15:10')
;




select
  ClientID
  ,min(RecordDateTime) as [Occurrence Start]
  ,max(RecordDateTime) as [Occurrence End]
from
(
select
  ClientID
  ,RecordDateTime
  ,sum(grp) over(PARTITION BY ClientID ORDER BY RecordDateTime) as sgrp
from
  (
   select
       ClientID
       ,RecordDateTime
       ,isnull(prevRecordDT,RecordDateTime) as prevRecordDT
      ,case when datediff(second,prevRecordDT,RecordDateTime) &lt;=60 then 0 else 1 end as grp
  from
    (
    select
          ClientID, RecordDateTime,
          LAG(RecordDateTime,1,NULL)OVER(PARTITION BY ClientID ORDER BY RecordDateTime) as prevRecordDT
    from Table1  
    ) as s
  ) as g
) as a
group by ClientID,sgrp


output of it:

ClientID    Occurrence Start    Occurrence End
1   14/02/2019 14:05:49 14/02/2019 14:07:19
1   14/02/2019 14:08:49 14/02/2019 14:10:32
1   14/02/2019 14:12:32 14/02/2019 14:12:32
1   14/02/2019 14:14:18 14/02/2019 14:15:10


dbfiddle
 source of inspiration

A short description:

select
      ClientID, RecordDateTime,
      LAG(RecordDateTime,1,NULL)OVER(PARTITION BY ClientID ORDER BY RecordDateTime) as prevRecordDT
from Table1 


key point here is the LAG function , to get the previous value

ClientID    RecordDateTime  prevRecordDT
1   14/02/2019 14:05:49 
1   14/02/2019 14:06:34 14/02/2019 14:05:49
1   14/02/2019 14:07:19 14/02/2019 14:06:34


Then, do a difference, in seconds , to test if it's in interval:
,case when datediff(second,prevRecordDT,RecordDateTime) &lt;= 60 then 0 else 1 end as grp 

select
       ClientID
       ,RecordDateTime
       ,isnull(prevRecordDT,RecordDateTime) as prevRecordDT
      ,case when datediff(second,prevRecordDT,RecordDateTime) &lt;= 60 then 0 else 1 end as grp
  from
       (
          select
               ClientID, RecordDateTime,
               LAG(RecordDateTime,1,NULL)OVER(PARTITION BY ClientID ORDER BY RecordDateTime) as prevRecordDT
          from Table1  
        ) as s

ClientID    RecordDateTime  prevRecordDT    grp
1   14/02/2019 14:05:49 14/02/2019 14:05:49 1
1   14/02/2019 14:06:34 14/02/2019 14:05:49 0
1   14/02/2019 14:07:19 14/02/2019 14:06:34 0
1   14/02/2019 14:08:49 14/02/2019 14:07:19 1


After this, just do a sum base on grp column
,sum(grp) over(PARTITION BY ClientID ORDER BY RecordDateTime) as sgrp

select
  ClientID
  ,RecordDateTime
  ,sum(grp) over(PARTITION BY ClientID ORDER BY RecordDateTime) as sgrp
from
  (
   select
       ClientID
       ,RecordDateTime
       ,isnull(prevRecordDT,RecordDateTime) as prevRecordDT
      ,case when datediff(second,prevRecordDT,RecordDateTime) &lt;= 60 then 0 else 1 end as grp
  from
    (
    select
          ClientID, RecordDateTime,
          LAG(RecordDateTime,1,NULL)OVER(PARTITION BY ClientID ORDER BY RecordDateTime) as prevRecordDT
    from Table1  
    ) as s
  ) as g

ClientID    RecordDateTime      sgrp
1         14/02/2019 14:05:49   1
1         14/02/2019 14:06:34   1
1         14/02/2019 14:07:19   1
1         14/02/2019 14:08:49   2
1         14/02/2019 14:09:34   2


And finally, do min and max grouping by ClientID and sgrp