How to convert string timestamp into timestamp with a specific timezone

Question

I'm trying to convert string timestamp having timezone in it to a timestamp with the same timezone. However, when executing the below code, I'm getting default system timestamp. Can someone help me on this. Below is the code I'm trying.

try {
    Date dt = new Date();
    SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
    f.setTimeZone(TimeZone.getTimeZone("GMT"));
    String dateString = f.format(dt);
    System.out.println("DateString: "+dateString);
    Date parsedDate = f.parse(dateString);
    System.out.println("ParsedDate: "+parsedDate);
    Timestamp timestamp = new Timestamp(parsedDate.getTime());
    System.out.println("Timestamp: "+timestamp);
    
}catch (Exception e) {
    // TODO: handle exception
}

When executing the above code, I get below result:

DateString: 2021-03-26T06:57:05.982+0000
ParsedDate: Fri Mar 26 12:27:05 IST 2021
Timestamp: 2021-03-26 12:27:05.982

But I have to get output in Timestamp as 2021-03-26T06:57:05.982+0000

Answer 1

Your code using java.time classes:

        ZonedDateTime zdt = ZonedDateTime.now();
        DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
        DateTimeFormatter dfGMT = df.withZone(ZoneId.of("GMT"));
        
        String dateString = dfGMT.format(zdt);
        System.out.println("DateString: "+dateString);
        
        ZonedDateTime parsedDate = ZonedDateTime.parse(dateString,dfGMT);
        System.out.println("ParsedDate: "+ parsedDate);
        Timestamp timestamp = Timestamp.from(parsedDate.toInstant());
        System.out.println("Zoned Timestamp: "+timestamp);
        
        //ignoring zone info from date string
        LocalDateTime ldt = LocalDateTime.from(dfGMT.parse(dateString));
        timestamp = Timestamp.valueOf(ldt);
        System.out.println("Zone stripped GMT timestamp: "+timestamp);
        
        
        ZonedDateTime zdt1 = ldt.atZone(ZoneId.of("GMT"));
        zdt1 = zdt1.withZoneSameInstant(ZoneId.of("America/Chicago"));
        timestamp = Timestamp.valueOf(zdt1.toLocalDateTime());
        System.out.println("Zone stripped CST timestamp: "+timestamp);

Output:

DateString: 2021-03-26T09:10:37.537+0000
ParsedDate: 2021-03-26T09:10:37.537Z[GMT]
Zoned Timestamp: 2021-03-26 14:40:37.537
Zone stripped GMT timestamp: 2021-03-26 09:10:37.537
Zone stripped CST timestamp: 2021-03-26 04:10:37.537

Answer 2

java.time and JDBC 4.2

You don't need any formatting, parsing nor conversion. To insert the current timestamp into your SQL database:

    OffsetDateTime currentTimestamp = OffsetDateTime.now(ZoneOffset.UTC);
    String sql = "insert into your_table(your_timestamp_with_time_zone_column) values (?);";
    try (PreparedStatement prepStmt = yourDatabaseConnection.prepareStatement(sql)) {
        prepStmt.setObject(1, currentTimestamp);
        prepStmt.executeUpdate();
    }