array Problem

[kunal.kb]

please help me out
i am having an array like:

var holiday=[
["2004","10_29"],
["2004","10_29"],
["2004","10_29"],
["2004","10_13"],
["2005","10_13"],
["2005","10_14"],
["2005","10_14"],
["2005","10_14"],
["2005","10_15"],
["2005","10_15"],
["2005","10_28"],
["0"]];

But i wnt the array to be like :
var holiday=[
["2004","10_20|10_13"],
["2005","10_13|10_14|10_15|10_28"],
["0","0"]];

i have tried array.join() but it is not helping out....
i am stuck up with the same problem.......

[PeejAvery]

What scripting language is this? Can you just format the dates like YYYY,MM,DD?