formating dates and calculating length of time

[SorenN]

I am trying to figure figure out how the length of time between two dates (an online and offline date).
First the facts: Windows7 & Excel2010, I have tried formatting the cells to 'Date' which does not help and I have 1000+ date ranges to calculate.
The formula I found to do this is =DAYS360(Start_date,End_Date), which gives me a number of days such as 1140. My problem is that my source dates are 8-13-10 not 8/13/10 and pulled from a cell containing text and the date.
Here is a copy of my data, formulas and results:

E4(source data)	G4(source data)	I4(formula)	I4(display)	J4(formula)	J4(display)	K4(Formula)	K4(Display)
Inst. 02-04-13	Off 01-22-14	=MID(E4,6,9)	02-04-13 <tbody> </tbody>	=IF(G4>0,MID(G4,4,9),"02-24-14")	06-30-13 <tbody> </tbody>	=DAYS360(I4,J4)	#VALUE! <tbody> </tbody>

<tbody>
</tbody>

What options do I have to calculate the date ranges? Do I need to change all "-" to "/" and if so can you give me a tip on how to do that en-mass?
Thanks you all so much for taking a stab at this! I have learned a lot already working on this project and look forward to learning more with your help!
-Soren

 

[mfexcel]

if you need to calculate the difference between two dates: a simple formula I4-J4 would do.
since the date is actually stored as text in your case, you may need:
=value(I4)-value(J4)

 

[SorenN]

Thanks a lot mfexcel! The results on my sample data are close to using =DAYS360 when dates are 02/15/09. They are close enough that I am not going to worry about it and calculate the results!