what time of day does the lunar new year start?
The Gregorian new year starts at 12 midnight local time and as far as I know there is no universal time such as 0000 hrs GMT worldwide. New year chimes and fireworks are specifically timed for 0000 hrs (2400 hrs) local time.
There seems to not be a convention as to the time of day when the lunar new year starts. As it is defined by a new moon there is no moonrise as such. Is there a convention such as a specific lunar event that defines the exact time, and is that definition based on a specific time zone, such as a specific location in China or on a local basis of the moon coordinates at each individual location?
This matters for example if a child is born on the eve or day of the lunar new year as the precise time (hours and minutes) should determine which side of the new year "moment" defines the year of birth.