unixEpochDate property
January 1st, 1970 is known as the Unix epoch. It is the date and time that Unix systems use as the reference point for measuring time. This date was chosen arbitrarily by early Unix engineers because they needed a uniform and convenient date for the start of time.
Implementation
// NOTE: default month and day == 1
static final DateTime unixEpochDate = DateTime.utc(1970);