Format Instant to String

Question

I m trying to format an Instant to a String using the new java 8 time-api and a pattern   Instant instant        String out   DateTimeFormatter ofPattern  yyyy-MM-dd HH mm ss   format instant     Using the code above I get an Exception which complains an unsupported field   java time temporal UnsupportedTemporalTypeException  Unsupported field  YearOfEra     at java time Instant getLong Instant java 608      at java time format DateTimePrintContext getValue DateTimePrintContext java 298

User · Answer

The Instant class doesn t contain Zone information  it only stores timestamp in milliseconds from UNIX epoch  i e  1 Jan 1070 from UTC  So  formatter can t print a date because date always printed for concrete time zone  You should set time zone to formatter and all will be fine  like this    Instant instant   Instant ofEpochMilli 92554380000L   DateTimeFormatter formatter   DateTimeFormatter ofLocalizedDateTime FormatStyle SHORT  withLocale Locale UK  withZone ZoneOffset UTC   assert formatter format instant  equals  07 12 72 05 33    assert instant toString   equals  1972-12-07T05 33 00Z

User · Answer

DateTimeFormatter ISO INSTANT format Instant now      This saves you from having to convert to UTC   However  some other language s time frameworks may not support the milliseconds so you should do   DateTimeFormatter ISO INSTANT format Instant now   truncatedTo ChronoUnit SECONDS

User · Answer

DateTimeFormatter formatter   DateTimeFormatter ofPattern  yyyy MM dd    String text   date toString formatter   LocalDate date   LocalDate parse text  formatter     I believe this might help  you may need to use some sort of localdate variation instead of instant

User · Answer

Instants are already in UTC and already have a default date format of yyyy-MM-dd  If you re happy with that and don t want to mess with time zones or formatting  you could also toString   it   Instant instant   Instant now    instant toString   output  2020-02-06T18 01 55 648475Z    Don t want the T and Z   Z indicates this date is UTC  Z stands for  Zulu  aka  Zero hour offset  aka UTC    instant toString   replaceAll   TZ         output  2020-02-06 18 01 55 663763    Want milliseconds instead of nanoseconds   So you can plop it into a sql query    instant truncatedTo ChronoUnit MILLIS  toString   replaceAll   TZ         output  2020-02-06 18 01 55 664   etc

User · Answer

Or if you still want to use formatter created from pattern you can just use LocalDateTime instead of Instant   LocalDateTime datetime   LocalDateTime now    DateTimeFormatter ofPattern  yyyy-MM-dd HH mm ss   format datetime

User · Answer

public static void main String   args         DateTimeFormatter DATE TIME FORMATTER   DateTimeFormatter ofPattern  yyyy-MM-dd HH mm ss                withZone ZoneId systemDefault          System out println DATE TIME FORMATTER format new Date   toInstant

User · Answer

Time Zone To format an Instant a time-zone is required  Without a time-zone  the formatter does not know how to convert the instant to human date-time fields  and therefore throws an exception  The time-zone can be added directly to the formatter using withZone    DateTimeFormatter formatter       DateTimeFormatter ofLocalizedDateTime  FormatStyle SHORT                         withLocale  Locale UK                         withZone  ZoneId systemDefault       If you specifically want an ISO-8601 format with no explicit time-zone  as the OP asked   with the time-zone implicitly UTC  you need DateTimeFormatter ISO LOCAL DATE TIME withZone ZoneId from ZoneOffset UTC    Generating String Now use that formatter to generate the String representation of your Instant  Instant instant   Instant now    String output   formatter format  instant     Dump to console  System out println  quot formatter   quot    formatter    quot  with zone   quot    formatter getZone      quot  and Locale   quot    formatter getLocale      System out println  quot instant   quot    instant    System out println  quot output   quot    output     When run  formatter  Localized SHORT SHORT  with zone  US Pacific and Locale  en GB instant  2015-06-02T21 34 33 616Z output  02 06 15 14 34

[java] Format Instant to String

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