Front End Submit, Events off by 1month

Tracked it down. You use moment.js , which converts the date string into a unix timestamp.
And the unix timestamp is wrong.

Whether this is your fault or moment.js fault is to be determined.
I unminified your minified script which is injected into the loaded singular javascript file on page load. Then added some console.log to it, and began debugging.
Below is the code altered that proves the unix timestamp returned from moment.js is WRONG by 1 month.

y = function() {
                    var t = e("#ai1ec-start-date-input",
                            f),
                        n = e("#ai1ec-end-date-input",
                            f),
                        r = e("#ai1ec-start-time-input",
                            f),
                        i = e("#ai1ec-end-time-input",
                            f),
                        s = e("#ai1ec-has-time",
                            f)[0].checked,
                        o = t.val(),
                        a = r.val(),
                        l = n.val(),
                        c = i.val(),
                        h = "",
                        p = "",
                        d,
                        v,
                        m,
                        g = f.data("ai1ecStartTime"),
                        y = f.data("ai1ecEndTime"),
                        b = !1;
						console.log('t: ');console.log(t);
                    typeof g == "undefined" && (g = ""),
                        typeof y == "undefined" && (y = ""),
                        d = t.data("dateFormat").toUpperCase(),
                        r.data("showMeridian") ? v = "hh:mm A" : v = "HH:mm",
                        m = d + " " + v,
                        o !== "" && (s && a !== "" ? h = u(o + " " + a,m) : h = u(o,d),
                            h = h.unix()),
                        h === "" || g !== "" && parseInt(g,
                            10) === h ? l !== "" && (s && c !== "" ? p = u(l + " " + c,
                                m) : p = u(l,
                                d),
                            p = p.unix(),
                            p < h && (p = h,
                                b = !0)) : (g === "" ? g = h : g = parseInt(g,
                                10),
                            y === "" ? y = g : y = parseInt(y,
                                10),
                            p = h + y - g,
                            b = !0);
                    if (b) {
                        var w = u.unix(p);
                        n.val(w.format(d)).datepicker("update").datepicker("setStartDate",
                                o),
                            s && a !== "" && i.val(w.format(v))
                    }
					console.log('h: '+h); // INVALID TIMESTAMP 1 MONTH OFF
					try {
						console.log(u);// moment.js function.
						console.log(o);// the date string. ITS VALID. Not wrong.
						console.log(a); // unknown empty string
						console.log(m); // the date format.

						console.log('---------------------------');
						console.log('1: '+(u(o + " " + a,m))); // timestamp 1, both identical, both wrong
						console.log('2: '+ (u(o,d))); // timestamp 2 , both identical, both wrong
						console.log('3: '+ (h.unix())); // null, not used, unknown.
					}catch(e) {console.log(e);}

                    f.data("ai1ecStartTime",
                            h),
                        f.data("ai1ecEndTime", p)

Proof that it is caused inside moment.js, which by the way is a very old version of it.
(wp-content/plugins/all-in-one-event-calendar/public/js/external_libs/moment.js)
This is console output. You can see that it returns the wrong date 90% of the time.

$
$(e, t)
$(t="6/10/2015",n)
Fri Jul 10 2015 00:00:00 GMT-0500 (Central Daylight Time)

$(t="5/10/2015",n)
Sun May 10 2015 00:00:00 GMT-0500 (Central Daylight Time)

$(t="6/10/2015",n)
Fri Jul 10 2015 00:00:00 GMT-0500 (Central Daylight Time)

$(t="4/10/2015",n)
Sun May 10 2015 00:00:00 GMT-0500 (Central Daylight Time)

$(t="1/10/2015",n)
Sat Jan 10 2015 00:00:00 GMT-0600 (Central Standard Time)

$(t="2/10/2015",n)
Tue Mar 10 2015 00:00:00 GMT-0500 (Central Daylight Time)

$(t="02/10/2015",n)
Tue Mar 10 2015 00:00:00 GMT-0500 (Central Daylight Time)

$(t="02/10/2015",n="MM/DD/YYYY")
Tue Mar 10 2015 00:00:00 GMT-0500 (Central Daylight Time)

$(t="22/10/2015",n="MM/DD/YYYY")
Mon Oct 10 2016 00:00:00 GMT-0500 (Central Daylight Time)

$(t="00/10/2015",n="MM/DD/YYYY")
Wed Dec 10 2014 00:00:00 GMT-0600 (Central Standard Time)

$(t="01/10/2015",n="MM/DD/YYYY")
Sat Jan 10 2015 00:00:00 GMT-0600 (Central Standard Time)

$(t="02/10/2015",n="MM/DD/YYYY")
Tue Mar 10 2015 00:00:00 GMT-0500 (Central Daylight Time)

$(t="03/10/2015",n="MM/DD/YYYY")
Tue Mar 10 2015 00:00:00 GMT-0500 (Central Daylight Time)

The following function is causing the malfunction

moment.js, unminified, cleaned, rewritten:

function I(e, t, n, r) {
    var i, s, o = [];
    for (i = 0; i < 7; i++) {
        o[i] = e[i] = e[i] == null ? i === 2 ? 1 : 0 : e[i];
    }

	o[7] = t;
	e[7] = o[7];
	if (e[8] != null) {
		o[8] = e[8];
	}
	if (n) {
		e[3]+=n;
	} else e[3]=0;
	if (r) {
		e[4]+=r;
	} else e[4]=0;
	s = new Date(0);
	if (t) {
		s.setYear(e[0]);
		s.setUTCMonth(e[1]);
		s.setUTCDate(e[2]);
		s.setUTCHours(e[3], e[4], e[5], e[6]);
	} else {
		s.setYear(e[0]);
		s.setMonth(e[1]); // THIS ONE DOES IT.
		s.setDate(e[2]);
		s.setHours(e[3], e[4], e[5], e[6]);
	}
	s._a = o;
    return s;
}

So I am going to have to modify moment.js in your plugin to fix this, and stop wordpress from updating your software at this time unfortunately.

When I whittled it down, the following code in chrome browser console reproduces the problem:

s = new Date(0); s.setYear(2015); s
Thu Dec 31 2015 18:00:00 GMT-0600 (Central Standard Time)

s.setMonth(5); s
Wed Jul 01 2015 18:00:00 GMT-0500 (Central Daylight Time)

s.setMonth(6); s
Wed Jul 01 2015 18:00:00 GMT-0500 (Central Daylight Time)

Please explain that.

So for anyone having this issue. Change this code:
new Date(0)

To this:
new Date()

Problem solved.

https://stackoverflow.com/questions/30788920/javascript-date-function-abnormalities

Hi,

In a few days we will release an upgrade and this bug will be fixed.

Wonderful, thank you for the support!

No problem ??

Hi Benjamin,

A month ago you said this issue would be resolved in a few days… Can we ever expect an update that will make this calendar usable again?

Please advise.