Date Difference

Srinivas_Itech So basically MTBF. If you really need them in the exact order, then you will need an index (second example). PBIX is attached below signature.

Diff Days = 
    VAR __LogDate = [Log Date]
    VAR __Order = [Order ID]
    VAR __PrevLogDate = MAXX(FILTER('Table',[Order ID] = __Order && [Log Date] < __LogDate),[Log Date])
    VAR __PrevDate = MAXX(FILTER('Table',[Order ID] = __Order && [Log Date] = __PrevLogDate),[Close Date])
RETURN
    DATEDIFF(__PrevDate, __LogDate, DAY)

Diff Days 2 = 
    VAR __LogDate = [Log Date]
    VAR __Index = [Index]
    VAR __Order = [Order ID]
    VAR __Prev = MAXX(FILTER('Table',[Order ID] = __Order && [Index] < __Index),[Index])
    VAR __PrevDate = MAXX(FILTER('Table',[Order ID] = __Order && [Index] = __Prev),[Close Date])
RETURN
    DATEDIFF(__PrevDate, __LogDate, DAY)

See my article on Mean Time Between Failure (MTBF) which uses EARLIER: http://community.powerbi.com/t5/Community-Blog/Mean-Time-Between-Failure-MTBF-and-Power-BI/ba-p/339586.
The basic pattern is:
Column = 
  VAR __Current = [Value]
  VAR __PreviousDate = MAXX(FILTER('Table','Table'[Date] < EARLIER('Table'[Date])),[Date])

  VAR __Previous = MAXX(FILTER('Table',[Date]=__PreviousDate),[Value])
RETURN
  __Current - __Previous