new Date(xiYear, xiMonth, xiDate)
Apr 5th 00:00 GMT+01:00
Apr 4th 23:00 GMT+01:00
Apr 5th 01:00 GMT+01:00
.setUTCHours() it would be possible to actually set dates in UTC-time, which would allow you to use UTC-times throughout the system.
You cannot set it using UTC in the constructor though, unless you specify a date-string.
new Date(Date.UTC(year, month, day, hour, minute, second)) you can create a Date-object from a specific UTC time.