How to get the same output of departed Date.parse() in groovy?

Question

I have an application that runs the old version of the spring application. The application has the function to create date objects using Date.parse as follows

Date getCstTimeZoneDateNow() {
  String dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
  def zonedDateString = new Date().format(dateFormat, TimeZone.getTimeZone('CST'))
  Date date = Date.parse(dateFormat, zonedDateString)
  return date // Tue Oct 18 20:36:12 EDT 2022 (in Date)
}

However, the code above is deprecated. I need to produce the same result. I read other posts and it seems like Calender or SimpleDateFormatter is preferred. And I thought SimpleDateFormatter has more capabilities.

This post helped me understand more about what is going on in the following code SimpleDateFormat parse loses timezone

Date getCstTimeZoneDateNow() {
  Date now = new Date()
  String pattern = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"

  SimpleDateFormat sdf = new SimpleDateFormat()
  sdf.setTimeZone(TimeZone.getTimeZone('CST'))

  // cstDateTime prints times in cst
  String cstDateTime = sdf.format(now)  // 2022-10-18T20:36:12.088Z (in String)
  // JVM current time
  Date date = sdf.parse(cstDateTime) // Tue Oct 18 21:36:12 EDT 2022 (in Date)

  return date 
}

Here my goal is to return the date object that is in the format of Tue Oct 18 20:36:12 EDT 2022 The format is good. However, like the post says, when I do sdf.parse(), it prints in JVM time. This means, the format is good but the time zone is off. How can I get the exact same result as before? It does not have to use SimpleDateFormatter. Could be anything.

Thank you so much for reading and for your time.

Answer 1

Perhaps the important thing is, that the Date is always neutral to the timezone. Given example shows what is to be expected to work from the Java specs:

def format = new SimpleDateFormat()
format.setTimeZone(TimeZone.getTimeZone("CST"))
println new Date()
def date = format.parse(format.format(new Date()))
printf "parsed to %s%n", date
printf "formatted to %s (%s)%n", format.format(date), format.getTimeZone().getDisplayName()

In the output, notice when using the Format and when the toString(), a different time is shown accordingly, which is perfectly fine, since first we format and then parse again in the same format, thus the same time-zone. Later, we use the Date.toString() to output the date, this time using the system default time-zone which is always used when Date.toString() is called. In the output, the time-zone shift is reflected:

Thu Oct 20 09:22:58 EDT 2022
parsed to Thu Oct 20 09:22:00 EDT 2022
formatted to 10/20/22 8:22 AM (Central Standard Time)