记录将根据美国的时区保存,但如果我想向用户显示相同的记录,则应将服务器日期时间(美国时区)转换为用户的时区的用户日期时间
If you type in google "Java date change timezone" or "Javascript date change timezone". You will have one of your results:
In Java (source: http://www.coderanch.com/t/417443/java/java/Convert-Date-one-timezone-another )
Date date = new Date();
DateFormat formatter = new SimpleDateFormat("dd MMM yyyy HH:mm:ss z");
formatter.setTimeZone(TimeZone.getTimeZone("CET"));
// Prints the date in the CET timezone
System.out.println(formatter.format(date));
// Set the formatter to use a different timezone
formatter.setTimeZone(TimeZone.getTimeZone("IST"));
// Prints the date in the IST timezone
System.out.println(formatter.format(date));
Javascript (source: http://www.techrepublic.com/article/convert-the-local-time-to-another-time-zone-with-this-javascript/6016329 )
// function to calculate local time
// in a different city
// given the city's UTC offset
function calcTime(city, offset) {
// create Date object for current location
d = new Date();
// convert to msec
// add local time zone offset
// get UTC time in msec
utc = d.getTime() + (d.getTimezoneOffset() * 60000);
// create new Date object for different city
// using supplied offset
nd = new Date(utc + (3600000*offset));
// return time as a string
return "The local time in " + city + " is " + nd.toLocaleString();
}
// get Bombay time
alert(calcTime('Bombay', '+5.5'));
The old date-time classes are poorly designed, confusing, and troublesome. Avoid them.
Use modern classes: the java.time framework built into Java 8 and later. Find back-ports for earlier Java 6 & 7 and for Android .
An Instant
is a moment on the timeline in UTC .
Instant now = Instant.now();
Apply a time zone ( ZoneId
) to get a ZonedDateTime
.
Never use the 3-4 letter zone abbreviations such as EST
or IST
. They are neither standardized nor unique(!). Use proper time zone names , built in a continent/region
format such as Asia/Kolkata
, Pacific/Auckland
, America/Los_Angeles
.
ZoneId zoneId_Montreal = ZoneId.of( "America/Montreal" );
ZonedDateTime zdt_Montreal = ZonedDateTime.ofInstant( instant , zoneId_Montreal );
Apply a different time zone to generate another ZonedDateTime
adjusted to that time zone. Call withZoneSameInstant
.
ZoneId zoneId_Paris = ZoneId.of( "Europe/Paris" ); // Or "Asia/Kolkata", etc.
ZonedDateTime zdt_Paris = zdt_Montreal.withZoneSameInstant( zoneId_Paris );
If you want to go back to UTC , ask for an Instant
.
Instant instant = zdt_Paris.toInstant();
TimeZone fromTimezone =TimeZone.getTimeZone(from);
TimeZone toTimezone=TimeZone.getTimeZone(to);
long fromOffset = fromTimezone.getOffset(calendar.getTimeInMillis());
long toOffset = toTimezone.getOffset(calendar.getTimeInMillis());
long convertedTime = calendar.getTimeInMillis() - (fromOffset - toOffset);
//Convert date from one zone to another
/*
$zone_from='Asia/Kolkata';
$zone_to='America/Phoenix';
date_default_timezone_set($zone_from);
$convert_date="2016-02-26 10:35:00";
echo $finalDate=zone_conversion_date($convert_date, $zone_from, $zone_to);
*/
function zone_conversion_date($time, $cur_zone, $req_zone)
{
date_default_timezone_set("GMT");
$gmt = date("Y-m-d H:i:s");
date_default_timezone_set($cur_zone);
$local = date("Y-m-d H:i:s");
date_default_timezone_set($req_zone);
$required = date("Y-m-d H:i:s");
/* return $required; */
$diff1 = (strtotime($gmt) - strtotime($local));
$diff2 = (strtotime($required) - strtotime($gmt));
$date = new DateTime($time);
$date->modify("+$diff1 seconds");
$date->modify("+$diff2 seconds");
return $timestamp = $date->format("Y-m-d H:i:s");
}
Code To Get Berlin Time and Convert it into UTC Time
Calendar sc = Calendar.getInstance(TimeZone.getTimeZone("Europe/Berlin"));
String strt = null;
SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm'Z'");
sf.setTimeZone(TimeZone.getTimeZone("Etc/UTC"));
sc.set(sc.get(Calendar.YEAR),sc.get(Calendar.MONTH), sc.get(Calendar.DATE),sc.get(Calendar.HOUR) , sc.get(Calendar.MINUTE));
strt = sf.format(sc.getTime());
System.out.println("Start :"+strt);
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