This was a funny exercise to play with...
Here is a code that does what you want :
function test(){
convertToDateArray('7/26,7/27-7/31,8/1,8/2,8/3-8/5');
}
function convertToDateArray(inputString){
if(typeof(inputString)=='string'){inputString=inputString.split(',')}; // if input is a string then split it into an array using comma as separator
var data = [];
var datesArray = [];
for(var n in inputString){
if(inputString[n].indexOf('-')==-1){inputString[n]+='-'};// if only 1 field add an empty one
data.push(inputString[n].split('-'));// make it an array
}
Logger.log(data);//check
for(var n in data){
var temp = [];
for(var c in data[n]){
Logger.log('data[n][c] = '+ data[n][c]);
var date = data[n][c]!=''? new Date(2014,Number(data[n][c].split('/')[0])-1,Number(data[n][c].split('/')[1]),0,0,0,0) : '';// create date objects with right values
Logger.log('date = '+date);//check
temp.push(date);
}
datesArray.push(temp);//store output data in an array of arrays, ready to setValues in a SS
}
Logger.log(datesArray);
var sh = SpreadsheetApp.getActive().getActiveSheet();
sh.getRange(1,1,datesArray.length,datesArray[0].length).setValues(datesArray);
}
Logger result for datesArray :
[[Sat Jul 26 00:00:00 GMT+02:00 2014, ], [Sun Jul 27 00:00:00 GMT+02:00 2014, Thu Jul 31 00:00:00 GMT+02:00 2014], [Fri Aug 01 00:00:00 GMT+02:00 2014, ], [Sat Aug 02 00:00:00 GMT+02:00 2014, ], [Sun Aug 03 00:00:00 GMT+02:00 2014, Tue Aug 05 00:00:00 GMT+02:00 2014]]