Date toString without timezone conversion for MessageFormat

Question

I'm using ibm's MessageFormat library to localize an incoming date.

The task here is to run a few checks on the date before showing it to the end user. I get a ZonedDateTime object and I need to make sure that it doesn't fall in the weekend, which I do using the getDayOfWeek.

My problem happens when I try to convert my date to a string using MessageFormat. Since MessageFormat accepts only java.util.Date objects, I convert my ZonedDateTime -> Instant -> Date. Unfortunately, this method results in my "Monday" becoming a "Sunday," as shown below.

I noticed that this "loss" happens upon the Date conversion. This is because the Date.toString() object is being invoked by MessageFormat, and the former uses the JVM's default timezone (in my case, PST). As a result, my UTC gets implicitly converted to a PST and I lose a day.

Any ideas how to tackle this? Is there anything else that I can pass to MessageFormat? Is there a way to use Date but not get this undesired behavior? Is there another localization library I can use?

Answer 1

Internally, MessageFormat uses a DateFormat object but does not allow you to set its timezone. @Assylias linked a question where the answer tries to pull out the internal DateFormat, set its timezone, and then use the MessageFormat as usual, which resolves the issue.

However, I found that to be too wordy, particularly because you have to create a new MessageFormat everytime (as opposed to reusing the MessageFormat that you already set the timezone for).

What I opted for was to simply use SimpleDateFormat directly.

// I have a ZonedDateTime zonedDateTime that I want to print out.
final SimpleDateFormat dateFormat = new SimpleDateFormat("EEEE, MM dd", locale);
dateFormat.setTimeZone(TimeZone.getTimeZone(zonedDateTime.getZone()));
final String formattedDateString = dateFormat.format(Date.from(zonedDateTime.toInstant()));

I then use String.format to insert my formatted date into a larger string. Hope this helps.