// takes the date encoded as milliseconds since midnight, January 1, 1970 UTC
def mydate = new Date(System.currentTimeMillis())

// create from an existing Calendar object
def mydate = new GregorianCalendar(2014, Calendar.APRIL, 3, 1, 23, 45).time

// uses the format strings from Java's SimpleDateFormat
def mydate = Date.parse("yyyy-MM-dd hh:mm:ss", "2014-04-03 1:23:45")

// uses a format equivalent to EEE MMM dd HH:mm:ss zzz yyyy
def mydate = Date.parseToStringDate("Thu Apr 03 01:23:45 UTC 2014")

def mydate = new Date().copyWith(
    year: 2014,
    month: Calendar.APRIL,
    dayOfMonth: 3,
    hourOfDay: 1,
    minute: 23,
    second: 45)

def calendar = new GregorianCalendar(2011,1,7,15,7,23)
def date = calendar.getTime()
println date