When a mobile touches a date on a calendar or a browser simulate a mobile click , the onclick event of the calendar gets called twice, also if you press a date of another month it has the chance of going 2 month because of it and from what i see it is in the dhtmlx.js the part where "this.contDates.onclick=function(w){ "
And from what i saw from a console.log i get a pointer event and a touch event
Please, check the dhtmlxSuite version you are using.
I was not able to reproduce your mentioned issue in the latest build (v5.2).
You can check it in the following snippet:
https://snippet.dhtmlx.com/5/8d37122b2
If the problem still occurs for you please, try to update your dhtmlxSuite/Calendar build or provide a complete demo, where the problem can be reproduce locally.
The snippet does not work on mobile or on the mobile simulation on desktop. Like for example, if you go on mobile it gets triggered twice or if you toggle device toolbar in the browser to simulate a mobile device it triggers the event twice and if you click on another month date like for example your calendar is in January and you click on the 5th February since it clicks twice it might go to the month of march if you are unable to reproduce it, i can send a video of me doing it on the snippet you sent me.