javascript - Result of toJSON() on a date is different between IE8 and IE9+ -

i'm doing conversion date string , using in sessionstorage. first this:

sessionstorage.currentdate = mydate.tojson(); 

and this:

if (sessionstorage.currentdate ) {     mydate = new date(sessionstorage.currentdate); } 

the problem mydate.tojson() function in ie9+ returns "2013-05-06t22:00:00.000z" in ie8 returns "2013-05-06t22:00:00z" missing decimal part @ end. fact in ie8 failing subsequent re-conversion date (the result new date(sessionstorage.currentdate) nan)

any idea why happening , how make code work ie8+?

update:

i tried replace string in debug, , turns out none of 2 strings works. seems problem of new date(sessionstorage.currentdate) not recognizing format (wich utc)

prior es5, parsing of dates entirely implementation dependent. ie 8 (and lower) won't parse iso 8601 format specified in es5, parse yourself:

// parse iso format date 2013-05-06t22:00:00.000z function datefromiso(s) {   s = s.split(/\d/);   return new date(date.utc(s[0], --s[1]||'', s[2]||'', s[3]||'', s[4]||'', s[5]||'', s[6]||'')) } 

assumes string utc.