Google Chrome 49.0.2623.110 (64-bit)

I'm not sure, but I have a feeling that it could be related to ZBX-10060

Kim, is this reproducible only if you play with the Leap day ?

vitalijs.cemeris Seems that this issue is not related.

Oleksiy, Oh, Thanks. I didn't know that issue. So I checked play with more rows. I added more screenshot now.

then now... I think 2 issue was different.
This case, not only 'Very first records' -　this happened 'All or part of datas stored before in a database.'
UI says Item start from '3/29' was completely different and this problem is user can't change history stored date from UI.

Kim, thanks !
No problems, it happens sometime that some issue reports, which are not related at first glance, actually caused by the same reason.
So it worth sometime to mention them and discuss to make sure they are different

Oleksiy, Thanks!
Yes. I agree with you. Of course, It may be also a cause same reason. I don't know much about javascript and I have not seen source, but this case I suspect common problems for getMonth values. (0~11) or.. end of month?
and I need a little more time to this comments system.

I play with more this problem, and I confirmed that there are more problems with some other days.

If your data from 2/29, set the clock change…

・Data started “2/29” - Set the clock “3/29” = OK
・Data started “2/29” - Set the clock “3/30” = WRONG (UI says, from 3/29)
・Data started “2/29” - Set the clock “3/31” = WRONG (UI says, from 3/29)

・Data started “2/29” - Set the clock “4/29” = OK
・Data started “2/29” - Set the clock “4/30” = WRONG (UI says, from 3/29)

・Data started “2/29” - Set the clock “5/29” = OK
・Data started “2/29” - Set the clock “5/30” = WRONG (UI says, from 3/29)
・Data started “2/29” - Set the clock “5/31” = WRONG (UI says, from 3/29)

In these cases, There's a possibility of this trouble may come “EVERY end of Month” (Actually, over 30~)

And more, Data started time change…

Jan
・Data started “1/29” - Set the clock “3/30” = OK 

Feb (Leap year)
・Data started  “2/1” - Set the clock “3/30” = WRONG (UI says, from 3/1)
・Data started  “2/2” - Set the clock “3/30” = WRONG (UI says, from 3/2)
・Data started  “2/11” - Set the clock “3/30” = WRONG (UI says, from 3/11)
・Data started  “2/22” - Set the clock “3/30” = WRONG (UI says, from 3/22)
・Data started  “2/28” - Set the clock “3/30” = WRONG (UI says, from 3/28)
・Data started  “2/29” - Set the clock “3/30” = WRONG (UI says, from 3/29)

Mar
・Data started  “3/29” - Set the clock “3/30” = OK
・Data started  “3/29” - Set the clock “4/30” = OK

Feb (2015)
・Data started  “2/28” - Set the clock “3/31” = WRONG (UI says, from 3/28)

So, I think there is a strong possibility that from All day of the February.
(2016/4/8 Issue title changed. 'Leap day' -> 'February')

Added : This 'Feb' start time changed to 'Mar' problem is possible to reproducible on Zabbix 3.0.1.
Strangely when I clicked the 'All' button, oldest 1 records disappeared occurs at correct time period in 3.0.1. I think that could be related to ZBX-10060. (2.2.11 wasn't disappeared & This is not only 'Feb')

(2016/4/15 Issue title changed. ‘February’ -> ‘End of month')

Sorry I'm a stranger here. I checked source and finally I feel like understand that.

When the day value is greater than the maximum number of days in the month passed to setMonth() in setZBXDate.
in this case, in setZBXDate will set the wrong value. start time ‘2016-02-29’ was changed to ’2016-03-29’
when you open the history page at the end of the month (3/30~31, 4/30, 5/30~31…)

I added javascript debug screenshot & explain comments below :

source : frontends/php/js/class.cdate.js - 147~149 lines (Zabbix 2.2.11)

 this.serverDate.setFullYear(theDate.Y);	 //this.serverDate already have ‘2016-03-30’
 this.serverDate.setMonth(theDate.m - 1);  //set Month. this.serverDate is now ‘2016-02-30’. but ’02/30’ does not exist. so changed to ’2016-03-01’
 this.serverDate.setDate(theDate.d); // set Day. this.serverDate is now ’2016-03-29’	
…

This is not limited to 'Feb’ start problem too. Actually, limited to “All day of the end of month”
For example, I confirmed start time ’2016-04-30’ was changed to ‘2016-05-30’. (on 5/31, 7/31, 8/31…)

Before to do set date in setZBXDate. It is necessary to check the day of month.

I was just thinking to resolve the invert the position of setMonth() & setDate() at first view, but this solution has another problem with some other days.
Because both functions can occur when the recalculated set greater than the maximum number of days.

FYI : If you use 3.0, can be possible to reproduce ‘very first record time datas’ disappeared. This issue can't fix this problem. It could be related to ZBX-10060.

In the case of Mar 31, it is set for 31 days in Feb.

	setZBXDate: function(strdate) {
		this.server = 1;

		var theDate = {
			Y: strdate.toString().substr(0, 4),
			m: strdate.toString().substr(4, 2),
			d: strdate.toString().substr(6, 2),
			H: strdate.toString().substr(8, 2),
			i: strdate.toString().substr(10, 2),
			s: strdate.toString().substr(12, 2)
		};

		this.serverDate.setFullYear(theDate.Y);
		this.serverDate.setMonth(theDate.m - 1); <-- Feb.
		this.serverDate.setDate(theDate.d);      <-- 31  
		this.serverDate.setHours(theDate.H);
		this.serverDate.setMinutes(theDate.i);
		this.serverDate.setSeconds(theDate.s);
		this.serverDate.setMilliseconds(0);
		this.calcTZdiff();

		return this.getTime();
	},

This problem is solved by setting the month to the last.

	setZBXDate: function(strdate) {
		this.server = 1;

		var theDate = {
			Y: strdate.toString().substr(0, 4),
			m: strdate.toString().substr(4, 2),
			d: strdate.toString().substr(6, 2),
			H: strdate.toString().substr(8, 2),
			i: strdate.toString().substr(10, 2),
			s: strdate.toString().substr(12, 2)
		};

		this.serverDate.setFullYear(theDate.Y);
		this.serverDate.setDate(theDate.d);
		this.serverDate.setHours(theDate.H);       
		this.serverDate.setMinutes(theDate.i);
		this.serverDate.setSeconds(theDate.s);
		this.serverDate.setMonth(theDate.m - 1);   <-- here!
		this.serverDate.setMilliseconds(0);
		this.calcTZdiff();

		return this.getTime();
	},

Thanks to fix code. I said this before,

I was just thinking to resolve the invert the position of setMonth() & setDate() at first view, but this solution has another problem with some other days.

Sorry for the lack of explanation. I was confirmed "~ ENDTIME(now!)" was changed to 'before’ on end of month.
So I tried to reproduce this. but... I don't know why, I can't reproduce this time.
When there is no problem in the recheck this, it is all right.

Closed as duplicated by ZBX-10866.