zdump Command

Purpose

Displays the time zone information.

Syntax

zdump [--version] [--help] [-v] [-V] [-c [loyear,]hiyear] [-t [lotime,]hitime] [ -i ] zonename ...

Description

The zdump command prints the time zone information for each zone name that is specified in the command line.

Flags

Table 1. Flags
Item	Description
-c [`loyear`,]`hiyear`	Reports the verbose output for the specified years. Cutoff time is computed by using the proleptic Gregorian calendar with year 0 and Universal Time (UT) ignoring leap seconds. The smaller year attribute (`loyear`) is exclusive and the higher year attribute (`hiyear`) is inclusive. For example, a `loyear` value of 1970 excludes a transition that occurs at 1970-01-01 00:00:00 Coordinated Universal Time, but a `hiyear` value of 1970 includes the transition. The default cutoff time is -500,2500.
--help	Displays a short usage message and exits.
-i	Provides a list of all the transitions and displays a description of the time intervals. For each time zone on the command line, the -i flag displays an interval format description of the time zone. For more information, see the Interval format section.
-t [`lotime`,]`hitime`	Reports verbose output for a particular time that is specified in the `lotime` and `hitime` attributes in the syntax of `yyyy-mm-dd hh:mm:ss` Coordinated Universal Time (UTC). For example, 1970-01-01 00:00:00. The cutoff time includes the leap seconds depending on the `zonename` parameter. Similar to the -c flag, the smaller time limit is exclusive and the higher time limit is inclusive.
-v	For each zone name that is specified in the command line, the zdump command prints the following items: The lowest possible value of time. The time at one day after the lowest possible value of time. The times both one second before and exactly at each detected discontinuity of time. The highest possible value of time. The time at one day before the highest possible value of time. Each line is followed by `isdst=D`, where `D` is a positive, zero, or negative value that depends on whether the specified time is Daylight Saving Time, standard time, or an unknown time type. Each line is also followed by `gmtoff=N`, where the specified local time is `N` seconds east of Greenwich.
-V	Prints an output that is similar to the output of the -v flag except that this flag does not display the times that are relative to the extreme time values. This flag generates output that is simpler to compare with different time representations.
--version	Displays the version information of the zdump command.

Parameters

Table 2. Parameters
Item	Description
`zonename`	Represents the name of the zone of which the time zone information is displayed.

Interval format

The interval format is a compact text representation of transitions for a specified time zone that is both human and machine readable. The interval format representation starts with a line TZ=string, where string is the time zone for which the transition data is displayed. The time zone information for each transition is displayed in a tabular format with the date, time, and interval columns. The first entry in the table displays a value only for the interval column as it refers to the time interval before first transition.

The values of the date column are in yyyy-mm-dd format, and the values of the time column are in hh:mm:ss format. The time is the local time immediately after the transition. The interval column consists of a UT offset in ±hhmmss format, a time zone abbreviation, and an isdst flag. A positive value of the UT offset indicates that the time zone is in the east of UT, and a negative value indicates that the time zone is in the west of UT. The UT offset value of -00 denotes a UT placeholder in areas where the actual offset is not specified. The value of UT offset is -00 when the UT offset is zero and the time zone abbreviation begins with - or is zzz. The time zone abbreviation that is equal to the UT offset is omitted. For the standard time, the isdst flag is omitted. The value of the isdst flag is a positive decimal integer (usually 1) for the daylight saving and is a negative decimal integer for an unknown value.

The following examples shows the interval format representation of transitions for a specified time zone:


TZ="Pacific/Honolulu"
-           -         -103126  LMT
1896-01-13  12:01:26  -1030    HST
1933-04-30  03        -0930    HDT  1
1933-05-21  11        -1030    HST
1942-02-09  03        -0930    HWT  1
1945-08-14  13:30     -0930    HPT  1
1945-09-30  01        -1030    HST
1947-06-08  02:30     -10      HST

The TZ="Pacific/Honolulu" indicates that the time zone is Pacific/Honolulu. The first row entry in the interval format representation indicates that the local time is 10 hours, 31 mins, and 26 secs west of UT and the standard time abbreviation is LMT. The next row indicates that the date of transition is 13 January 1896, the time of transition is 12:01:26, the time interval is 10 hours, 30 mins west of UT, and the standard time abbreviation is HST. The isdst flag value of 1 in the third entry indicates Daylight Saving Time.

Exit Status

0: The command was completed successfully.
>0: An error occurred.

Examples

To report time zone information for Singapore, enter the following command:
```
zdump -v Singapore
```
To display time zone information for Turkiye stopping near the start of the year 2035, enter the following command:
```
zdump -v -c 2035 Turkey
```

To report the time zone information for New York during the years 2015 - 2017, enter the following command:

zdump -v -c 2015,2017 America/New_York

The output is similar to the following sample:

America/New_York  Fri Dec 13 20:45:52 1901 UT = Fri Dec 13 15:45:52 1901 EST isdst=0 gmtoff=-18000
America/New_York  Sat Dec 14 20:45:52 1901 UT = Sat Dec 14 15:45:52 1901 EST isdst=0 gmtoff=-18000
America/New_York  Sun Mar  8 06:59:59 2015 UT = Sun Mar  8 01:59:59 2015 EST isdst=0 gmtoff=-18000
America/New_York  Sun Mar  8 07:00:00 2015 UT = Sun Mar  8 03:00:00 2015 EDT isdst=1 gmtoff=-14400
America/New_York  Sun Nov  1 05:59:59 2015 UT = Sun Nov  1 01:59:59 2015 EDT isdst=1 gmtoff=-14400
America/New_York  Sun Nov  1 06:00:00 2015 UT = Sun Nov  1 01:00:00 2015 EST isdst=0 gmtoff=-18000
America/New_York  Sun Mar 13 06:59:59 2016 UT = Sun Mar 13 01:59:59 2016 EST isdst=0 gmtoff=-18000
America/New_York  Sun Mar 13 07:00:00 2016 UT = Sun Mar 13 03:00:00 2016 EDT isdst=1 gmtoff=-14400
America/New_York  Sun Nov  6 05:59:59 2016 UT = Sun Nov  6 01:59:59 2016 EDT isdst=1 gmtoff=-14400
America/New_York  Sun Nov  6 06:00:00 2016 UT = Sun Nov  6 01:00:00 2016 EST isdst=0 gmtoff=-18000
America/New_York  Mon Jan 18 03:14:07 2038 UT = Sun Jan 17 22:14:07 2038 EST isdst=0 gmtoff=-18000
America/New_York  Tue Jan 19 03:14:07 2038 UT = Mon Jan 18 22:14:07 2038 EST isdst=0 gmtoff=-18000

To report the time zone information for New York during the years 2015 - 2017 without the lowest and highest time values, enter the following command:

zdump -V -c 2015,2017 America/New_York

The output is similar to the following sample:

America/New_York  Sun Mar  8 06:59:59 2015 UT = Sun Mar  8 01:59:59 2015 EST isdst=0 gmtoff=-18000
America/New_York  Sun Mar  8 07:00:00 2015 UT = Sun Mar  8 03:00:00 2015 EDT isdst=1 gmtoff=-14400
America/New_York  Sun Nov  1 05:59:59 2015 UT = Sun Nov  1 01:59:59 2015 EDT isdst=1 gmtoff=-14400
America/New_York  Sun Nov  1 06:00:00 2015 UT = Sun Nov  1 01:00:00 2015 EST isdst=0 gmtoff=-18000
America/New_York  Sun Mar 13 06:59:59 2016 UT = Sun Mar 13 01:59:59 2016 EST isdst=0 gmtoff=-18000
America/New_York  Sun Mar 13 07:00:00 2016 UT = Sun Mar 13 03:00:00 2016 EDT isdst=1 gmtoff=-14400
America/New_York  Sun Nov  6 05:59:59 2016 UT = Sun Nov  6 01:59:59 2016 EDT isdst=1 gmtoff=-14400
America/New_York  Sun Nov  6 06:00:00 2016 UT = Sun Nov  6 01:00:00 2016 EST isdst=0 gmtoff=-18000

Files

Table 3. Files
Item	Description
/usr/sbin/zdump	Contains the SystemV zdump command.
/usr/share/lib/zoneinfo	Contains the standard time zone directory.