This is usage of Date object on Groovy2.1 Groovy2.1でのDateオブジェクトの使い方です。

date_sample.groovy

// *******************************************
// This is usage of Date object on Groovy2.1
// Groovy2.1でのDateオブジェクトの使い方です。
// *******************************************

// Generate Date object.(Default TimeZone is "CET" in my computer)
// Dateオブジェクトの生成(私の環境ではデフォルトのタイムゾーンは"CET")
// sample of how to declare
// def sample = new Date()
// def sample = Date.parse("yyyy/MM/dd HH:mm:ss", "1985/02/20 12:34:56")
// def sample = new Date("1985/02/20 12:34:56")
def today = new Date("2013/02/01 12:34:56")
assert today.format("yyyy/MM/dd HH:mm:ss z") == "2013/02/01 12:34:56 CET"

// change the TimeZone from CET to Japan when the display.
// 表示時にタイムゾーンをCETからJapanに変更
assert today.format("yyyy/MM/dd HH:mm:ss z", TimeZone.getTimeZone("Japan")) == "2013/02/01 20:34:56 JST"

// change the date and time in Date object.(future)
// I used "clone()" for assert for check variable. of course you can use "new Date()" too.
// Dateオブジェクトの日時を変更(future)
// assertで中身を確認する為に"clone()"を使いました。もちろん"new Date()"でもかまいません。
def future = today.clone()
assert future.format("yyyy/MM/dd HH:mm:ss z") == "2013/02/01 12:34:56 CET"

use(groovy.time.TimeCategory){
	future = future + 2.year
	future = future + 2.month
	future = future + 2.day
	future = future + 2.hour
	future = future + 2.minute
	future = future + 2.second
}

// calculated date and time in Date object.(future)
// Achtung!
// Why has changed to "CEST" timezone?
// Because this future date and time is summer time.
// Dateオブジェクトの日時の計算結果(future)
assert future.format("yyyy/MM/dd HH:mm:ss z") == "2015/04/03 14:36:58 CEST"

// difference of today and future.(Number of days)
// todayとfutureの差分（日数）
assert future.minus(today) == 791

// difference of today and future.(Number of second)
// todayとfutureの差分（秒数）
def msec = future.toTimestamp().getTime() - today.toTimestamp().getTime()
assert msec / 1000 == 68346122