converting seconds into time ?

Hi I am converting seconds into time and I used the following formula:

=FormatNumber(Floor([Elapsed Time]/3600) ;"0") + ":" +

FormatNumber(Floor(Mod([Elapsed Time];3600)/60);"00") + ":" +

FormatNumber(Mod(Mod([Elapsed Time] ;3600) ;60) ;"00")

The problem I now have is it is giving time as

0:02:50 1350:07:59 :: 0:11:15 5:05:35 359:55:49 :: 0:01:33 6:32:38 :: 0:04:20 0:25:53 3:38:58 72:00:04 :: 0:02:32 0:16:19 3:41:01

How do I convert something like second row above 1350:07:59 as days which is 56.

Please help.

Thanks,