The Start and End Date Time should be set based on the UTC, ISO, and Central Time zones

This JavaScript code is designed for Dynamics 365 CRM, specifically for the Date Time fields for Start and End Date Time. It runs when the Scheduled Start (scheduledstart) field changes and adjusts both the start and end date time to cover the entire day in UTC, ISO, and Central time.

Login to D365
Create a JavaScript web resource in D365
Open an appointment entity form
Registered an event on
scheduledstart Onchange Event Trigger
Apy.Field.onChange("scheduledstart", setStartAndEndDateTime);

This line registers the function Name setStartAndEndDateTime to execute whenever the Scheduled Start field (scheduledstart) changes.

Create a JavaScript web resource in D365

Registered an

setStartAndEndDateTime: function () {
    var globalContext = Xrm.Utility.getGlobalContext();
    var userId = globalContext.userSettings.userId.replace(/[{}]/g, "");
    var timeZoneCode = 0;

    Xrm.WebApi.online.retrieveMultipleRecords(
        "usersettings",
        "?$select=timezonecode&$filter=systemuserid eq " + userId
    )
        .then(function (result) {
            if (result.entities.length > 0) {
                timeZoneCode = result.entities[0].timezonecode;
                var startDate =
                    Apy.Field.getValue("scheduledstart") == null
                        ? new Date()
                        : new Date(Apy.Field.getValue("scheduledstart"));

                startDate = new Date(startDate);
                var startDateTime, endDateTime;
                var startDay, endDay;

                if (timeZoneCode == 190) {
                    startDateTime = Apy.Appointment.convertToUTC(
                        new Date(startDate.getFullYear(), startDate.getMonth(), startDate.getDate(), 0, 0, 0),
                        "Asia/Kolkata"
                    );
                    endDateTime = Apy.Appointment.convertToUTC(
                        new Date(startDate.getFullYear(), startDate.getMonth(), startDate.getDate(), 23, 59, 0),
                        "Asia/Kolkata"
                    );
                } else if (timeZoneCode === 92) {
                    var timeZoneOffset = startDate.getTimezoneOffset() * 60000;
                    startDay = new Date(startDate.getFullYear(), startDate.getMonth(), startDate.getDate(), 0, 0, 0);
                    endDay = new Date(startDate.getFullYear(), startDate.getMonth(), startDate.getDate(), 23, 59, 0);
                    startDateTime = new Date(startDay.getTime() - timeZoneOffset);
                    endDateTime = new Date(endDay.getTime() - timeZoneOffset);
                } else if (timeZoneCode == 20 || timeZoneCode == 35 || timeZoneCode == 33) {
                    startDateTime = new Date(
                        Date.UTC(startDate.getFullYear(), startDate.getMonth(), startDate.getDate(), 6, 0, 0)
                    );
                    endDateTime = new Date(
                        Date.UTC(startDate.getFullYear(), startDate.getMonth(), startDate.getDate(), 29, 59, 0)
                    );
                }

                Apy.Field.setValue("scheduledstart", startDateTime);
                Apy.Field.setValue("scheduledend", endDateTime);
            }
        })
        .catch(function (error) {
            Xrm.Utility.alertDialog(error);
        });
},

convertToUTC: function (date, timeZone) {
    return new Date(date.toLocaleString("en-US", { timeZone: timeZone }));
},