Java Utililty Methods TimeZone Usage

long addGmtOffset(long millis)
add Gmt Offset

return millis + localTimeZone.getOffset(millis);

void assertTimeZoneNotNull(String methodName, TimeZone timeZone)
assert Time Zone Not Null

if (timeZone == null) {
 String msg = "The argument 'timeZone' should not be null: method=" + methodName;
 throw new IllegalArgumentException(msg);

TimeZone buildTimezone(int hours, int minutes)
Builds a timezone object with the given offset.

int hourMillis = 1000 * 60 * 60 * hours;
int minuteMillis = 1000 * 60 * minutes;
if (hours < 0) {
 minuteMillis *= -1;
return new SimpleTimeZone(hourMillis + minuteMillis, "");

int computeTimeZoneOffsetInHours(TimeZone timeZone, long currentDatetime)
Computes the offset in hours for a given timezone at a given date/time.

int offsetInMilliseconds = timeZone.getOffset(currentDatetime);
return offsetInMilliseconds / (1000 * 60 * 60);

String createPostgresTimeZone()
Convert Java time zone to postgres time zone.

String tz = TimeZone.getDefault().getID();
if (tz.length() <= 3 || !tz.startsWith("GMT")) {
 return tz;
char sign = tz.charAt(3);
String start;
if (sign == '+') {
 start = "GMT-";
...

TimeZone createTaiTimeZone(int leapSecs)
create Tai Time Zone

return new SimpleTimeZone(leapSecs * 1000, "TAI");

Date datePlusDays(Date date, int days)
date Plus Days

Calendar calendar = getMoscowCalendar();
calendar.setTime(date);
calendar.add(Calendar.DAY_OF_YEAR, days);
return calendar.getTime();

TimeZone findTimeZoneInDate(String date)
find Time Zone In Date

StringBuilder sb = new StringBuilder();
StringBuilder dateBuilder = new StringBuilder(date.trim()).reverse();
int index = 0;
char c;
while ((c = dateBuilder.charAt(index++)) != ' ') {
 sb.append(c);
TimeZone timezone = TimeZone.getTimeZone(sb.reverse().toString());
...

boolean isInEasternEightZones()
is In Eastern Eight Zones

boolean defaultVaule = true;
if (TimeZone.getDefault() == TimeZone.getTimeZone("GMT+08"))
 defaultVaule = true;
else
 defaultVaule = false;
return defaultVaule;

boolean isKeepTimeZone(TimeZone tz)
is Keep Time Zone

if (tz.getID().startsWith("Africa")) { 
 return true;
} else if (tz.getID().startsWith("America")) { 
 return true;
} else if (tz.getID().startsWith("Antarctica")) { 
 return true;
} else if (tz.getID().startsWith("Asia")) { 
 return true;
...