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/*
 * Copyright © 2018 The GWT Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.gwtproject.i18n.client;

import java.util.HashMap;
import java.util.Map;
import org.gwtproject.i18n.shared.CustomDateTimeFormat;
import org.gwtproject.i18n.shared.cldr.DateTimeFormatInfo;
import org.gwtproject.i18n.shared.cldr.impl.DateTimeFormatInfoImpl_en;
import org.gwtproject.i18n.shared.cldr.impl.DateTimeFormatInfo_factory;

/**
 * Formats and parses dates and times using locale-sensitive patterns.
 *
 * Patterns
 *
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 * 
 * Symbol Meaning Presentation Example
G era designator Text AD
y year Number 1996
L standalone month in year Text or Number July (or) 07
M month in year Text or Number July (or) 07
d day in month Number 10
h hour in am/pm (1-12) Number 12
H hour in day (0-23) Number 0
m minute in hour Number 30
s second in minute Number 55
S fractional second Number 978
E day of week Text Tuesday
c standalone day of week Text Tuesday
a am/pm marker Text PM
k hour in day (1-24) Number 24
K hour in am/pm (0-11) Number 0
z time zone Text Pacific Standard Time(see comment)
Z time zone (RFC 822) Text -0800(See comment)
v time zone id Text America/Los_Angeles(See comment)
' escape for text Delimiter 'Date='
'' single quote Literal 'o''clock'
 *
 * The number of pattern letters influences the format, as follows:
 *
 * 

 *   Text
 *   
if 4 or more, then use the full form; if less than 4, use short or abbreviated form if it
 *       exists (e.g., "EEEE" produces "Monday", "EEE"
 *       produces "Mon")
 *   
Number
 *   
the minimum number of digits. Shorter numbers are zero-padded to this amount (e.g. if
 *       "m" produces "6", "mm" produces "06").
 *       Year is handled specially; that is, if the count of 'y' is 2, the Year will be truncated to
 *       2 digits. (e.g., if "yyyy" produces "1997", "yy"
 *       produces "97".) Unlike other fields, fractional seconds are padded on the
 *       right with zero.
 *   
Text or Number
 *   
3 or more, use text, otherwise use number. (e.g. "M" produces "1"
 *       , "MM" produces "01", "MMM" produces "Jan"
 *       , and "MMMM" produces "January". Some pattern letters also
 *       treat a count of 5 specially, meaning a single-letter abbreviation: L, M
 *       , E, and c.
 * 
 *
 * Any characters in the pattern that are not in the ranges of ['a '..'z
 * '] and ['A'..'Z'] will be treated as quoted text. For instance,
 * characters like ':', ' .', ' ' (space), '#'
 * and ' @' will appear in the resulting time text even they are not embraced within
 * single quotes.
 *
 * 
[Time Zone Handling] Web browsers don't provide all the information we need for proper time
 * zone formating -- so GWT has a copy of the required data, for your convenience. For simpler
 * cases, one can also use a fallback implementation that only keeps track of the current timezone
 * offset. These two approaches are called, respectively, Common TimeZones and Simple TimeZones,
 * although both are implemented with the same TimeZone class.
 *
 * 
"TimeZone createTimeZone(String timezoneData)" returns a Common TimeZone object, and "TimeZone
 * createTimeZone(int timeZoneOffsetInMinutes)" returns a Simple TimeZone object. The one provided
 * by OS fall into to Simple TimeZone category. For formatting purpose, following table shows the
 * behavior of GWT DateTimeFormat.
 *
 * 
 * 
 * 
 * 
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 * 
 * Pattern Common TimeZone Simple TimeZone
z, zz, zzz PDT UTC-7
zzzz Pacific Daylight Time UTC-7
Z, ZZ -0700 -0700
ZZZ -07:00 -07:00
ZZZZ GMT-07:00 GMT-07:00
v, vv, vvv, vvvv America/Los_Angeles Etc/GMT+7
 *
 * Parsing Dates and Times
 *
 * The pattern does not need to specify every field. If the year, month, or day is missing from
 * the pattern, the corresponding value will be taken from the current date. If the month is
 * specified but the day is not, the day will be constrained to the last day within the specified
 * month. If the hour, minute, or second is missing, the value defaults to zero.
 *
 * 
As with formatting (described above), the count of pattern letters determines the parsing
 * behavior.
 *
 * 

 *   Text
 *   
4 or more pattern letters--use full form, less than 4--use short or abbreviated form if one
 *       exists. In parsing, we will always try long format, then short.
 *   
Number
 *   
the minimum number of digits.
 *   
Text or Number
 *   
3 or more characters means use text, otherwise use number
 * 
 *
 * Although the current pattern specification doesn't not specify behavior for all letters, it
 * may in the future. It is strongly discouraged to use unspecified letters as literal text without
 * quoting them.
 *
 * 
[Note on TimeZone] The time zone support for parsing is limited. Only standard GMT and RFC
 * format are supported. Time zone specification using time zone id (like America/Los_Angeles), time
 * zone names (like PST, Pacific Standard Time) are not supported. Normally, it is too much a burden
 * for a client application to load all the time zone symbols. And in almost all those cases, it is
 * a better choice to do such parsing on server side through certain RPC mechanism. This decision is
 * based on particular use cases we have studied; in principle, it could be changed in future
 * versions.
 *
 * 
Examples
 *
 * 
 * 
 * 
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 * 
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 * 
 * Pattern Formatted Text
"yyyy.MM.dd G 'at' HH:mm:ss vvvv" 1996.07.10 AD at 15:08:56 America/Los_Angeles
"EEE, MMM d, ''yy" Wed, July 10, '96
"h:mm a" 12:08 PM
"hh 'o''clock' a, zzzz"  12 o'clock PM, Pacific Daylight Time
"K:mm a, vvvv"  0:00 PM, America/Los_Angeles
"yyyyy.MMMMM.dd GGG hh:mm aaa" 01996.July.10 AD 12:08 PM
 *
 * Additional Parsing Considerations
 *
 * When parsing a date string using the abbreviated year pattern ( "yy"), the parser
 * must interpret the abbreviated year relative to some century. It does this by adjusting dates to
 * be within 80 years before and 20 years after the time the parser instance is created. For
 * example, using a pattern of "MM/dd/yy" and a DateTimeFormat object
 * created on Jan 1, 1997, the string "01/11/12" would be interpreted as Jan 11, 2012
 * while the string "05/04/64" would be interpreted as May 4, 1964. During parsing,
 * only strings consisting of exactly two digits, as defined by {@link Character#isDigit(char)},
 * will be parsed into the default century. If the year pattern does not have exactly two 'y'
 * characters, the year is interpreted literally, regardless of the number of digits. For example,
 * using the pattern "MM/dd/yyyy", "01/11/12" parses to Jan 11, 12 A.D.
 *
 * 
When numeric fields abut one another directly, with no intervening delimiter characters, they
 * constitute a run of abutting numeric fields. Such runs are parsed specially. For example, the
 * format "HHmmss" parses the input text "123456" to 12:34:56, parses the input text "12345" to
 * 1:23:45, and fails to parse "1234". In other words, the leftmost field of the run is flexible,
 * while the others keep a fixed width. If the parse fails anywhere in the run, then the leftmost
 * field is shortened by one character, and the entire run is parsed again. This is repeated until
 * either the parse succeeds or the leftmost field is one character in length. If the parse still
 * fails at that point, the parse of the run fails.
 *
 * 
In the current implementation, timezone parsing only supports GMT:hhmm, 
 * GMT:+hhmm, and GMT:-hhmm.
 *
 * 
Example
 *
 * {@example com.google.gwt.examples.DateTimeFormatExample}
 *
 * deprecated use {@link org.gwtproject.i18n.shared.DateTimeFormat} instead
 */
// Temporarily remove deprecation to keep from breaking teams that don't allow
// deprecated references.
// @Deprecated
public class DateTimeFormat extends org.gwtproject.i18n.shared.DateTimeFormat {

  /**
   * Predefined date/time formats -- see {@link CustomDateTimeFormat} if you need some format that
   * isn't supplied here.
   *
   * 
deprecated use {@link org.gwtproject.i18n.shared.DateTimeFormat.PredefinedFormat} instead
   */
  // Temporarily remove deprecation to keep from breaking teams that don't allow
  // deprecated references.
  // @Deprecated
  public enum PredefinedFormat {

    // TODO(jat): Javadoc to explain these formats

    /**
     * ISO 8601 date format, fixed across all locales.
     *
     * 
Example: {@code 2008-10-03T10:29:40.046-04:00}
     *
     * 
http://code.google.com/p/google-web-toolkit/issues/detail?id=3068
     *
     * 
http://www.iso.org/iso/support/faqs/faqs_widely_used_standards/widely_used_standards_other/date_and_time_format.htm
     */
    ISO_8601,

    /**
     * RFC 2822 date format, fixed across all locales.
     *
     * 
Example: {@code Thu, 20 May 2010 17:54:50 -0700}
     *
     * 
http://tools.ietf.org/html/rfc2822#section-3.3
     */
    RFC_2822,

    DATE_FULL,
    DATE_LONG,
    DATE_MEDIUM,
    DATE_SHORT,

    TIME_FULL,
    TIME_LONG,
    TIME_MEDIUM,
    TIME_SHORT,

    DATE_TIME_FULL,
    DATE_TIME_LONG,
    DATE_TIME_MEDIUM,
    DATE_TIME_SHORT,

    DAY,
    HOUR_MINUTE,
    HOUR_MINUTE_SECOND,
    HOUR24_MINUTE,
    HOUR24_MINUTE_SECOND,
    MINUTE_SECOND,
    MONTH,
    MONTH_ABBR,
    MONTH_ABBR_DAY,
    MONTH_DAY,
    MONTH_NUM_DAY,
    MONTH_WEEKDAY_DAY,
    YEAR,
    YEAR_MONTH,
    YEAR_MONTH_ABBR,
    YEAR_MONTH_ABBR_DAY,
    YEAR_MONTH_DAY,
    YEAR_MONTH_NUM,
    YEAR_MONTH_NUM_DAY,
    YEAR_MONTH_WEEKDAY_DAY,
    YEAR_QUARTER,
    YEAR_QUARTER_ABBR,
  }

  private static final Map cache;

  static {
    cache = new HashMap();
  }

  /**
   * Get a DateTimeFormat instance for a predefined format.
   *
   * 
See {@link CustomDateTimeFormat} if you need a localized format that is not supported here.
   *
   * @param predef {@link PredefinedFormat} describing desired format
   * @return a DateTimeFormat instance for the specified format
   */
  public static DateTimeFormat getFormat(PredefinedFormat predef) {
    if (usesFixedEnglishStrings(predef)) {
      String pattern;
      switch (predef) {
        case RFC_2822:
          pattern = org.gwtproject.i18n.shared.DateTimeFormat.RFC2822_PATTERN;
          break;
        case ISO_8601:
          pattern = org.gwtproject.i18n.shared.DateTimeFormat.ISO8601_PATTERN;
          break;
        default:
          throw new IllegalStateException("Unexpected predef type " + predef);
      }
      return getFormat(pattern, new DateTimeFormatInfoImpl_en());
    }
    DateTimeFormatInfo dtfi = getDefaultDateTimeFormatInfo();
    String pattern;
    switch (predef) {
      case DATE_FULL:
        pattern = dtfi.dateFormatFull();
        break;
      case DATE_LONG:
        pattern = dtfi.dateFormatLong();
        break;
      case DATE_MEDIUM:
        pattern = dtfi.dateFormatMedium();
        break;
      case DATE_SHORT:
        pattern = dtfi.dateFormatShort();
        break;
      case DATE_TIME_FULL:
        pattern = dtfi.dateTimeFull(dtfi.timeFormatFull(), dtfi.dateFormatFull());
        break;
      case DATE_TIME_LONG:
        pattern = dtfi.dateTimeLong(dtfi.timeFormatLong(), dtfi.dateFormatLong());
        break;
      case DATE_TIME_MEDIUM:
        pattern = dtfi.dateTimeMedium(dtfi.timeFormatMedium(), dtfi.dateFormatMedium());
        break;
      case DATE_TIME_SHORT:
        pattern = dtfi.dateTimeShort(dtfi.timeFormatShort(), dtfi.dateFormatShort());
        break;
      case DAY:
        pattern = dtfi.formatDay();
        break;
      case HOUR24_MINUTE:
        pattern = dtfi.formatHour24Minute();
        break;
      case HOUR24_MINUTE_SECOND:
        pattern = dtfi.formatHour24MinuteSecond();
        break;
      case HOUR_MINUTE:
        pattern = dtfi.formatHour12Minute();
        break;
      case HOUR_MINUTE_SECOND:
        pattern = dtfi.formatHour12MinuteSecond();
        break;
      case MINUTE_SECOND:
        pattern = dtfi.formatMinuteSecond();
        break;
      case MONTH:
        pattern = dtfi.formatMonthFull();
        break;
      case MONTH_ABBR:
        pattern = dtfi.formatMonthAbbrev();
        break;
      case MONTH_ABBR_DAY:
        pattern = dtfi.formatMonthAbbrevDay();
        break;
      case MONTH_DAY:
        pattern = dtfi.formatMonthFullDay();
        break;
      case MONTH_NUM_DAY:
        pattern = dtfi.formatMonthNumDay();
        break;
      case MONTH_WEEKDAY_DAY:
        pattern = dtfi.formatMonthFullWeekdayDay();
        break;
      case TIME_FULL:
        pattern = dtfi.timeFormatFull();
        break;
      case TIME_LONG:
        pattern = dtfi.timeFormatLong();
        break;
      case TIME_MEDIUM:
        pattern = dtfi.timeFormatMedium();
        break;
      case TIME_SHORT:
        pattern = dtfi.timeFormatShort();
        break;
      case YEAR:
        pattern = dtfi.formatYear();
        break;
      case YEAR_MONTH:
        pattern = dtfi.formatYearMonthFull();
        break;
      case YEAR_MONTH_ABBR:
        pattern = dtfi.formatYearMonthAbbrev();
        break;
      case YEAR_MONTH_ABBR_DAY:
        pattern = dtfi.formatYearMonthAbbrevDay();
        break;
      case YEAR_MONTH_DAY:
        pattern = dtfi.formatYearMonthFullDay();
        break;
      case YEAR_MONTH_NUM:
        pattern = dtfi.formatYearMonthNum();
        break;
      case YEAR_MONTH_NUM_DAY:
        pattern = dtfi.formatYearMonthNumDay();
        break;
      case YEAR_MONTH_WEEKDAY_DAY:
        pattern = dtfi.formatYearMonthWeekdayDay();
        break;
      case YEAR_QUARTER:
        pattern = dtfi.formatYearQuarterFull();
        break;
      case YEAR_QUARTER_ABBR:
        pattern = dtfi.formatYearQuarterShort();
        break;
      default:
        throw new IllegalArgumentException("Unexpected predefined format " + predef);
    }
    return getFormat(pattern, dtfi);
  }

  /**
   * Returns a DateTimeFormat object using the specified pattern. If you need to format or parse
   * repeatedly using the same pattern, it is highly recommended that you cache the returned 
   * DateTimeFormat object and reuse it rather than calling this method repeatedly.
   *
   * 
Note that the pattern supplied is used as-is -- for example, if you supply "MM/dd/yyyy" as
   * the pattern, that is the order you will get the fields, even in locales where the order is
   * different. It is recommended to use {@link #getFormat(PredefinedFormat)} instead -- if you use
   * this method, you are taking responsibility for localizing the patterns yourself.
   *
   * @param pattern string to specify how the date should be formatted
   * @return a DateTimeFormat object that can be used for format or parse date/time
   *     values matching the specified pattern
   * @throws IllegalArgumentException if the specified pattern could not be parsed
   */
  public static DateTimeFormat getFormat(String pattern) {
    return getFormat(pattern, getDefaultDateTimeFormatInfo());
  }

  /**
   * Retrieve the DateTimeFormat object for full date format. The pattern for this format is
   * predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link PredefinedFormat#DATE_FULL}
   *     instead
   */
  @Deprecated
  public static DateTimeFormat getFullDateFormat() {
    return getFormat(PredefinedFormat.DATE_FULL);
  }

  /**
   * Retrieve the DateTimeFormat object for full date and time format. The pattern for this format
   * is predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link
   *     PredefinedFormat#DATE_TIME_FULL} instead
   */
  @Deprecated
  public static DateTimeFormat getFullDateTimeFormat() {
    return getFormat(PredefinedFormat.DATE_TIME_FULL);
  }

  /**
   * Retrieve the DateTimeFormat object for full time format. The pattern for this format is
   * predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link PredefinedFormat#TIME_FULL}
   *     instead
   */
  @Deprecated
  public static DateTimeFormat getFullTimeFormat() {
    return getFormat(PredefinedFormat.TIME_FULL);
  }

  /**
   * Retrieve the DateTimeFormat object for long date format. The pattern for this format is
   * predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link PredefinedFormat#DATE_LONG}
   *     instead
   */
  @Deprecated
  public static DateTimeFormat getLongDateFormat() {
    return getFormat(PredefinedFormat.DATE_LONG);
  }

  /**
   * Retrieve the DateTimeFormat object for long date and time format. The pattern for this format
   * is predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link
   *     PredefinedFormat#DATE_TIME_LONG} instead
   */
  @Deprecated
  public static DateTimeFormat getLongDateTimeFormat() {
    return getFormat(PredefinedFormat.DATE_TIME_LONG);
  }

  /**
   * Retrieve the DateTimeFormat object for long time format. The pattern for this format is
   * predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link PredefinedFormat#TIME_LONG}
   *     instead
   */
  @Deprecated
  public static DateTimeFormat getLongTimeFormat() {
    return getFormat(PredefinedFormat.TIME_LONG);
  }

  /**
   * Retrieve the DateTimeFormat object for medium date format. The pattern for this format is
   * predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link PredefinedFormat#DATE_MEDIUM}
   *     instead
   */
  @Deprecated
  public static DateTimeFormat getMediumDateFormat() {
    return getFormat(PredefinedFormat.DATE_MEDIUM);
  }

  /**
   * Retrieve the DateTimeFormat object for medium date and time format. The pattern for this format
   * is predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link
   *     PredefinedFormat#DATE_TIME_MEDIUM} instead
   */
  @Deprecated
  public static DateTimeFormat getMediumDateTimeFormat() {
    return getFormat(PredefinedFormat.DATE_TIME_MEDIUM);
  }

  /**
   * Retrieve the DateTimeFormat object for medium time format. The pattern for this format is
   * predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link PredefinedFormat#TIME_MEDIUM}
   *     instead
   */
  @Deprecated
  public static DateTimeFormat getMediumTimeFormat() {
    return getFormat(PredefinedFormat.TIME_MEDIUM);
  }

  /**
   * Retrieve the DateTimeFormat object for short date format. The pattern for this format is
   * predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link PredefinedFormat#DATE_SHORT}
   *     instead
   */
  @Deprecated
  public static DateTimeFormat getShortDateFormat() {
    return getFormat(PredefinedFormat.DATE_SHORT);
  }

  /**
   * Retrieve the DateTimeFormat object for short date and time format. The pattern for this format
   * is predefined for each locale.
   *
   * @return A DateTimeFormat object
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link
   *     PredefinedFormat#DATE_TIME_SHORT} instead
   */
  @Deprecated
  public static DateTimeFormat getShortDateTimeFormat() {
    return getFormat(PredefinedFormat.DATE_TIME_SHORT);
  }

  /**
   * Retrieve the DateTimeFormat object for short time format. The pattern for this format is
   * predefined for each locale.
   *
   * @return A DateTimeFormat object.
   * @deprecated use {@link #getFormat(PredefinedFormat)} with {@link PredefinedFormat#TIME_SHORT}
   *     instead
   */
  @Deprecated
  public static DateTimeFormat getShortTimeFormat() {
    return getFormat(PredefinedFormat.TIME_SHORT);
  }

  /**
   * Internal factory method that provides caching.
   *
   * @param pattern
   * @param dtfi
   * @return DateTimeFormat instance
   */
  protected static DateTimeFormat getFormat(String pattern, DateTimeFormatInfo dtfi) {
    DateTimeFormatInfo defaultDtfi = getDefaultDateTimeFormatInfo();
    DateTimeFormat dtf = null;
    if (dtfi == defaultDtfi) {
      dtf = cache.get(pattern);
    }
    if (dtf == null) {
      dtf = new DateTimeFormat(pattern, dtfi);
      if (dtfi == defaultDtfi) {
        cache.put(pattern, dtf);
      }
    }
    return dtf;
  }

  private static DateTimeFormatInfo getDefaultDateTimeFormatInfo() {
    return DateTimeFormatInfo_factory.create();
  }

  /**
   * Returns true if the predefined format is one that specifies always using English
   * names/separators.
   *
   * This should be a method on PredefinedFormat, but that would defeat the enum optimizations
   * GWT is currently capable of.
   *
   * @param predef
   * @return true if the specified format requires English names/separators
   */
  private static boolean usesFixedEnglishStrings(PredefinedFormat predef) {
    switch (predef) {
      case RFC_2822:
        return true;
      case ISO_8601:
        return true;
      default:
        return false;
    }
  }

  /**
   * Constructs a format object using the specified pattern and the date time constants for the
   * default locale.
   *
   * @param pattern string pattern specification
   */
  protected DateTimeFormat(String pattern) {
    this(pattern, getDefaultDateTimeFormatInfo());
  }

  /**
   * Constructs a format object using the specified pattern and user-supplied date time constants.
   *
   * @param pattern string pattern specification
   * @param dtfi DateTimeFormatInfo instance to use
   */
  protected DateTimeFormat(String pattern, DateTimeFormatInfo dtfi) {
    super(pattern, dtfi);
  }
}
Pattern	Formatted Text
`"yyyy.MM.dd G 'at' HH:mm:ss vvvv"`	`1996.07.10 AD at 15:08:56 America/Los_Angeles`
`"EEE, MMM d, ''yy"`	`Wed, July 10, '96`
`"h:mm a"`	`12:08 PM`
`"hh 'o''clock' a, zzzz"`	`12 o'clock PM, Pacific Daylight Time`
`"K:mm a, vvvv"`	`0:00 PM, America/Los_Angeles`
`"yyyyy.MMMMM.dd GGG hh:mm aaa"`	`01996.July.10 AD 12:08 PM`
Symbol	Meaning	Presentation	Example
`G`	era designator	Text	`AD`
`y`	year	Number	`1996`
`L`	standalone month in year	Text or Number	`July (or) 07`
`M`	month in year	Text or Number	`July (or) 07`
`d`	day in month	Number	`10`
`h`	hour in am/pm (1-12)	Number	`12`
`H`	hour in day (0-23)	Number	`0`
`m`	minute in hour	Number	`30`
`s`	second in minute	Number	`55`
`S`	fractional second	Number	`978`
`E`	day of week	Text	`Tuesday`
`c`	standalone day of week	Text	`Tuesday`
`a`	am/pm marker	Text	`PM`
`k`	hour in day (1-24)	Number	`24`
`K`	hour in am/pm (0-11)	Number	`0`
`z`	time zone	Text	`Pacific Standard Time(see comment)`
`Z`	time zone (RFC 822)	Text	`-0800(See comment)`
`v`	time zone id	Text	`America/Los_Angeles(See comment)`
`'`	escape for text	Delimiter	`'Date='`
`''`	single quote	Literal	`'o''clock'`
Pattern	Common TimeZone	Simple TimeZone
z, zz, zzz	PDT	UTC-7
zzzz	Pacific Daylight Time	UTC-7
Z, ZZ	-0700	-0700
ZZZ	-07:00	-07:00
ZZZZ	GMT-07:00	GMT-07:00
v, vv, vvv, vvvv	America/Los_Angeles	Etc/GMT+7