JS calculates the incorrect number of days for the two date and time difference

Do a time countdown and find that the days are always incorrect.

JS Code:

1 //Define target Date2 varTargettime =NewDate ();3 4 //Target Date5Targettime.setfullyear (2015,5,1);6 7 //Target when8Targettime.sethours (12);9 Ten //Target points OneTargettime.setminutes (0); A  - //Target seconds -Targettime.setseconds (0); the  - //Target milliseconds -Targettime.setmilliseconds (0); -  + //converted to milliseconds - varEndTime =Targettime.gettime ();  +  A //Defining Methods at functionGetcountdowntime () { -         -             //define the date and time that the parameter returns today -             varNowtime =NewDate (); -              -             //Time Millisecond Difference in             varCOUNTDOWNMS = EndTime-nowtime.gettime (); -              to             //Get the time difference +             varCountdowndays = Math.floor (Countdownms/(1000 * 60 * 60 * 24 )); -  the             //To arrive at a time-hour difference *             varCountdownh = Math.floor (Countdownms/(1000 * 60 * 60))% 24; $ Panax Notoginseng             //To arrive at a time minute difference -             varCOUNTDOWNM = Math.floor (Countdownms/(1000 * 60))% 60; the  +             //To get a time difference of seconds A             varcountdowns = Math.floor (countdownms/1000)% 60; the             } +         }  -  $  $$ (document). Ready (function () { -Window.setinterval ("Getcountdowntime ()", 1000); -});

In the calculated number of days, the countdown is always different from the defined target date by about 30 days

// target date targettime.setfullyear (2015,5,1);

Here's the problem:

The three parameter of the setFullYear () method is Year,month,day, where month represents the number of months between 0~11.

So the target date of May 1, 2015 should be

// target date targettime.setfullyear (2015,4,1);

JS calculates the incorrect number of days for the two date and time difference