我遇到了帶有時區的日期格式，GMT但我不明白上述日期中微秒后的連字符部分是什么，以及兩種方式決議的格式是什么？

所以對于這個日期（沒有連字符）：，"2021-08-03T04:10:07.502"格式是YYYY-MM-dd'T'HH:mm:ss.SS

Q1：對于這個日期（帶連字符）：，"2021-08-03T04:10:07.502-0700"格式為：??

Q2：連字符部分是時區GMT嗎？

Q3：如果日期是微秒后的連字符形式，如何添加X個數字來解決它？

預期的Java代碼：

String dateFormatWithHyphen = "?"; // replace ? with that format
DateFormat dateFormat = new SimpleDateFormat(dateFormatWithHyphen);
dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
return dateFormat;

uj5u.com熱心網友回復：

tl;博士

輸入字串的圖表，包含日期、分隔符、時間和與 UTC 的偏移量。

2021-08-03T04:10:07.502-0700
  ^date^  ^   ^time^   ^offset
       separator

將您的日期與時間和從 UTC 的偏移量作為java.time.OffsetDateTime物件決議。

OffsetDateTime
.parse( 
    "2021-08-03T04:10:07.502-0700" , 
    new DateTimeFormatterBuilder()
    .parseLenient()
    .append( DateTimeFormatter.ISO_LOCAL_DATE_TIME )
    .appendPattern( "xx" )
    .toFormatter()
)
.toString()

2021-08-03T04:10:07.502-07:00

Q1：對于這個日期（帶連字符）：“2021-08-03T04:10:07.502-0700”，格式為：??

該字串采用標準ISO 8601格式。

但是，該字串省略了從 UTC 偏移的小時和分鐘之間的可選冒號字符。我建議始終包含該冒號，以實作機器的最大兼容性。冒號使它對人類來說也更具可讀性。所以使用這個：

2021-08-03T04:10:07.502-07:00

Q2：連字符部分是 GMT 時區嗎？

前面的 HYPHEN-MINUS 字符0700表示七個小時的偏移量在UTC 時間本初子午線之后。

- -07:00表示比 UTC 晚 7 小時，如在美洲所見。

• 07:00意味著比 UTC 提前 7 小時，如泰國、越南、印度尼西亞等亞洲地區所見。

UTC is the new GMT, practically speaking, with regard to common business-oriented situations. If you are doing rocket science or GPS/Galileo satellite calculations, you should research the difference. If you are programming for purchase orders and invoices, don't worry about it.

Regarding your phrase, “the timezone GMT”… that is a contradiction. UTC/GMT is not a time zone. It is the baseline against which offsets are defined: a certain number of hours-minutes-seconds. What longitude is to the prime meridian, offsets are to UTC. Time zones are much more. Time zones are a named history of the past, present, and future changes to the offset used by the people of a particular region as decided by politicians.

Q3: If the date is in with the hyphen form after microseconds, how can one add X number of digits to address it?

Actually, the .502 is milliseconds, not microseconds.

And no, the date is up front, the 2021-08-03 part, August 3rd, 2021.

The T separates the date portion from the time portion. The third portion is the offset of -07:00.

Code

You said:

DateFormat dateFormat = new SimpleDateFormat(dateFormatWithHyphen); dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));

You are using terrible date-time classes that were years ago supplanted by the modern java.time classes defined in java.time. Never use Date, Calendar, SimpleDateFormat, and such.

Use OffsetDateTime to represent a date with time-of-day as seen with a particular offset-from-UTC.

If your input included the optional COLON, we could simply do this:

String input = "2021-08-03T04:10:07.502-07:00" ;
OffsetDateTime odt = OffsetDateTime.parse( input ) ;

Without the COLON, we must specify a formatting pattern. We can build up a DateTimeFormatter object by using a DateTimeFormatterBuilder.

DateTimeFormatter f = 
    new DateTimeFormatterBuilder()
    .parseLenient()
    .append( DateTimeFormatter.ISO_LOCAL_DATE_TIME )
    .appendPattern( "xx" )
    .toFormatter()
;

Use that formatter.

OffsetDateTime odt = OffsetDateTime.parse( input , f ) ;

odt.toString(): 2021-08-03T04:10:07.502-07:00

Well, that code works. But the ideal solution would be convincing the publisher of your data to use the full ISO 8601 format including the COLON in every offset.

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