Spring's @DateTimeFormat produces a Date object with the previous day

Question

I've got a requestParam that takes in a date (ie. 2017-01-24T06:00:00.000Z).

I'm using DateTimeFormat to format it into a date to pass into my controller.

@DateTimeFormat(iso = DateTimeFormat.ISO.DATE) Date myDate 

but when I print myDate to my console I get "Mon Jan 23, 18:00:00 CST 2017", but in my example above it should be Jan 24th. Why is it changing my date back 1 day?

Answer 1

For me it works without @JsonFormat when json has the pattern 'yyyy-mm-dd'

@DateTimeFormat(iso = DateTimeFormat.ISO.DATE)
private LocalDate startDate;

Answer 2

There are several things at play here.

First, Spring's @DateTimeFormat, when annotating a java.util.Date field or parameter, uses a SimpleDateFormat with its timezone set to UTC.

Second, you've used DateTimeFormat.ISO.DATE which represents

The most common ISO Date Format yyyy-MM-dd, e.g. "2000-10-31".

In other words, it does not consider any timezone information in your date string (this doesn't really matter because your date string was rooted at Zulu anyway).

Third, you've provided a date string where everything but the iso pattern gets ignored. The SimpleDateFormat only cares about the 2017-01-24 part.

Since the timezone is set to UTC, it considers the 2017-01-24 date as being rooted at UTC, at midnight, zero'ed hours, minutes, and seconds.

Finally, since your system's default time zone is Central Standard Time, ie. UTC-6), when you call toString on the Date object, it'll return a String that is formatted with that time zone, ie. 6 hours before midnight.

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Remember also that a Date has no concept of a timezone. It is a timestamp.

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To "fix" this, construct your @DateTimeFormat with an appropriate pattern that interprets both time and time zone. I would use

@DateTimeFormat(pattern = "yyyy-MM-dd'T'HH:mm:ss.SSSX") Date myDate