MS-DOS date and time are packed 16-bit values that specify local date/time. The time is always stored in the current UTC time offset set on the computer which created the file. Note that the daylight saving time (DST) shifts also change the UTC time offset.
For example, if you pack two files A and B into a ZIP archive, file A last modified at 2020-03-29 00:59 UTC+00:00 (GMT) and file B at 2020-03-29 02:00 UTC+01:00 (BST), the file modification times saved in MS-DOS format in the ZIP file will vary depending on whether the computer packing the files is set to GMT or BST at the time of ZIP creation.
It follows that you are unable to determine the actual last modified time of any file stored in the ZIP archive, if you don't know the locale time setting of the computer at the time it created the ZIP.
This format is used in some data formats from the MS-DOS era, for example:
This page hosts a formal specification of MS-DOS datetime using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import io.kaitai.struct.ByteBufferKaitaiStream;
import io.kaitai.struct.KaitaiStruct;
import io.kaitai.struct.KaitaiStream;
import java.io.IOException;
import java.util.Objects;
import io.kaitai.struct.ConsistencyError;
/**
* MS-DOS date and time are packed 16-bit values that specify local date/time.
* The time is always stored in the current UTC time offset set on the computer
* which created the file. Note that the daylight saving time (DST) shifts
* also change the UTC time offset.
*
* For example, if you pack two files A and B into a ZIP archive, file A last modified
* at 2020-03-29 00:59 UTC+00:00 (GMT) and file B at 2020-03-29 02:00 UTC+01:00 (BST),
* the file modification times saved in MS-DOS format in the ZIP file will vary depending
* on whether the computer packing the files is set to GMT or BST at the time of ZIP creation.
*
* - If set to GMT:
* - file A: 2020-03-29 00:59 (UTC+00:00)
* - file B: 2020-03-29 01:00 (UTC+00:00)
* - If set to BST:
* - file A: 2020-03-29 01:59 (UTC+01:00)
* - file B: 2020-03-29 02:00 (UTC+01:00)
*
* It follows that you are unable to determine the actual last modified time
* of any file stored in the ZIP archive, if you don't know the locale time
* setting of the computer at the time it created the ZIP.
*
* This format is used in some data formats from the MS-DOS era, for example:
*
* - [zip](/zip/)
* - [rar](/rar/)
* - [vfat](/vfat/) (FAT12)
* - [lzh](/lzh/)
* - [cab](http://justsolve.archiveteam.org/wiki/Cabinet)
* @see <a href="https://learn.microsoft.com/en-us/windows/win32/sysinfo/ms-dos-date-and-time">Source</a>
* @see <a href="https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-dosdatetimetofiletime">Source</a>
* @see <a href="https://github.com/reactos/reactos/blob/c6b64448ce4/dll/win32/kernel32/client/time.c#L82-L87">DosDateTimeToFileTime</a>
* @see <a href="https://download.microsoft.com/download/0/8/4/084c452b-b772-4fe5-89bb-a0cbf082286a/fatgen103.doc">page 25/34</a>
*/
public class DosDatetime extends KaitaiStruct.ReadWrite {
public static DosDatetime fromFile(String fileName) throws IOException {
return new DosDatetime(new ByteBufferKaitaiStream(fileName));
}
public DosDatetime() {
this(null, null, null);
}
public DosDatetime(KaitaiStream _io) {
this(_io, null, null);
}
public DosDatetime(KaitaiStream _io, KaitaiStruct.ReadWrite _parent) {
this(_io, _parent, null);
}
public DosDatetime(KaitaiStream _io, KaitaiStruct.ReadWrite _parent, DosDatetime _root) {
super(_io);
this._parent = _parent;
this._root = _root == null ? this : _root;
}
public void _read() {
this.time = new Time(this._io, this, _root);
this.time._read();
this.date = new Date(this._io, this, _root);
this.date._read();
_dirty = false;
}
public void _fetchInstances() {
this.time._fetchInstances();
this.date._fetchInstances();
}
public void _write_Seq() {
_assertNotDirty();
this.time._write_Seq(this._io);
this.date._write_Seq(this._io);
}
public void _check() {
if (!Objects.equals(this.time._root(), _root()))
throw new ConsistencyError("time", _root(), this.time._root());
if (!Objects.equals(this.time._parent(), this))
throw new ConsistencyError("time", this, this.time._parent());
if (!Objects.equals(this.date._root(), _root()))
throw new ConsistencyError("date", _root(), this.date._root());
if (!Objects.equals(this.date._parent(), this))
throw new ConsistencyError("date", this, this.date._parent());
_dirty = false;
}
public static class Date extends KaitaiStruct.ReadWrite {
public static Date fromFile(String fileName) throws IOException {
return new Date(new ByteBufferKaitaiStream(fileName));
}
public Date() {
this(null, null, null);
}
public Date(KaitaiStream _io) {
this(_io, null, null);
}
public Date(KaitaiStream _io, DosDatetime _parent) {
this(_io, _parent, null);
}
public Date(KaitaiStream _io, DosDatetime _parent, DosDatetime _root) {
super(_io);
this._parent = _parent;
this._root = _root;
}
public void _read() {
this.day = this._io.readBitsIntLe(5);
if (!(this.day >= 1)) {
throw new KaitaiStream.ValidationLessThanError(1, this.day, this._io, "/types/date/seq/0");
}
this.month = this._io.readBitsIntLe(4);
if (!(this.month >= 1)) {
throw new KaitaiStream.ValidationLessThanError(1, this.month, this._io, "/types/date/seq/1");
}
if (!(this.month <= 12)) {
throw new KaitaiStream.ValidationGreaterThanError(12, this.month, this._io, "/types/date/seq/1");
}
this.yearMinus1980 = this._io.readBitsIntLe(7);
_dirty = false;
}
public void _fetchInstances() {
}
public void _write_Seq() {
_assertNotDirty();
this._io.writeBitsIntLe(5, this.day);
this._io.writeBitsIntLe(4, this.month);
this._io.writeBitsIntLe(7, this.yearMinus1980);
}
public void _check() {
if (!(this.day >= 1)) {
throw new KaitaiStream.ValidationLessThanError(1, this.day, null, "/types/date/seq/0");
}
if (!(this.month >= 1)) {
throw new KaitaiStream.ValidationLessThanError(1, this.month, null, "/types/date/seq/1");
}
if (!(this.month <= 12)) {
throw new KaitaiStream.ValidationGreaterThanError(12, this.month, null, "/types/date/seq/1");
}
_dirty = false;
}
private String paddedDay;
public String paddedDay() {
if (this.paddedDay != null)
return this.paddedDay;
this.paddedDay = (day() <= 9 ? "0" : "") + Long.toString(day());
return this.paddedDay;
}
public void _invalidatePaddedDay() { this.paddedDay = null; }
private String paddedMonth;
public String paddedMonth() {
if (this.paddedMonth != null)
return this.paddedMonth;
this.paddedMonth = (month() <= 9 ? "0" : "") + Long.toString(month());
return this.paddedMonth;
}
public void _invalidatePaddedMonth() { this.paddedMonth = null; }
private String paddedYear;
public String paddedYear() {
if (this.paddedYear != null)
return this.paddedYear;
this.paddedYear = (year() <= 999 ? "0" + (year() <= 99 ? "0" + (year() <= 9 ? "0" : "") : "") : "") + Long.toString(year());
return this.paddedYear;
}
public void _invalidatePaddedYear() { this.paddedYear = null; }
private Integer year;
/**
* only years from 1980 to 2107 (1980 + 127) can be represented
*/
public Integer year() {
if (this.year != null)
return this.year;
this.year = ((Number) (1980 + yearMinus1980())).intValue();
return this.year;
}
public void _invalidateYear() { this.year = null; }
private long day;
private long month;
private long yearMinus1980;
private DosDatetime _root;
private DosDatetime _parent;
public long day() { return day; }
public void setDay(long _v) { _dirty = true; day = _v; }
public long month() { return month; }
public void setMonth(long _v) { _dirty = true; month = _v; }
public long yearMinus1980() { return yearMinus1980; }
public void setYearMinus1980(long _v) { _dirty = true; yearMinus1980 = _v; }
public DosDatetime _root() { return _root; }
public void set_root(DosDatetime _v) { _dirty = true; _root = _v; }
public DosDatetime _parent() { return _parent; }
public void set_parent(DosDatetime _v) { _dirty = true; _parent = _v; }
}
public static class Time extends KaitaiStruct.ReadWrite {
public static Time fromFile(String fileName) throws IOException {
return new Time(new ByteBufferKaitaiStream(fileName));
}
public Time() {
this(null, null, null);
}
public Time(KaitaiStream _io) {
this(_io, null, null);
}
public Time(KaitaiStream _io, DosDatetime _parent) {
this(_io, _parent, null);
}
public Time(KaitaiStream _io, DosDatetime _parent, DosDatetime _root) {
super(_io);
this._parent = _parent;
this._root = _root;
}
public void _read() {
this.secondDiv2 = this._io.readBitsIntLe(5);
if (!(this.secondDiv2 <= 29)) {
throw new KaitaiStream.ValidationGreaterThanError(29, this.secondDiv2, this._io, "/types/time/seq/0");
}
this.minute = this._io.readBitsIntLe(6);
if (!(this.minute <= 59)) {
throw new KaitaiStream.ValidationGreaterThanError(59, this.minute, this._io, "/types/time/seq/1");
}
this.hour = this._io.readBitsIntLe(5);
if (!(this.hour <= 23)) {
throw new KaitaiStream.ValidationGreaterThanError(23, this.hour, this._io, "/types/time/seq/2");
}
_dirty = false;
}
public void _fetchInstances() {
}
public void _write_Seq() {
_assertNotDirty();
this._io.writeBitsIntLe(5, this.secondDiv2);
this._io.writeBitsIntLe(6, this.minute);
this._io.writeBitsIntLe(5, this.hour);
}
public void _check() {
if (!(this.secondDiv2 <= 29)) {
throw new KaitaiStream.ValidationGreaterThanError(29, this.secondDiv2, null, "/types/time/seq/0");
}
if (!(this.minute <= 59)) {
throw new KaitaiStream.ValidationGreaterThanError(59, this.minute, null, "/types/time/seq/1");
}
if (!(this.hour <= 23)) {
throw new KaitaiStream.ValidationGreaterThanError(23, this.hour, null, "/types/time/seq/2");
}
_dirty = false;
}
private String paddedHour;
public String paddedHour() {
if (this.paddedHour != null)
return this.paddedHour;
this.paddedHour = (hour() <= 9 ? "0" : "") + Long.toString(hour());
return this.paddedHour;
}
public void _invalidatePaddedHour() { this.paddedHour = null; }
private String paddedMinute;
public String paddedMinute() {
if (this.paddedMinute != null)
return this.paddedMinute;
this.paddedMinute = (minute() <= 9 ? "0" : "") + Long.toString(minute());
return this.paddedMinute;
}
public void _invalidatePaddedMinute() { this.paddedMinute = null; }
private String paddedSecond;
public String paddedSecond() {
if (this.paddedSecond != null)
return this.paddedSecond;
this.paddedSecond = (second() <= 9 ? "0" : "") + Long.toString(second());
return this.paddedSecond;
}
public void _invalidatePaddedSecond() { this.paddedSecond = null; }
private Integer second;
public Integer second() {
if (this.second != null)
return this.second;
this.second = ((Number) (2 * secondDiv2())).intValue();
return this.second;
}
public void _invalidateSecond() { this.second = null; }
private long secondDiv2;
private long minute;
private long hour;
private DosDatetime _root;
private DosDatetime _parent;
public long secondDiv2() { return secondDiv2; }
public void setSecondDiv2(long _v) { _dirty = true; secondDiv2 = _v; }
public long minute() { return minute; }
public void setMinute(long _v) { _dirty = true; minute = _v; }
public long hour() { return hour; }
public void setHour(long _v) { _dirty = true; hour = _v; }
public DosDatetime _root() { return _root; }
public void set_root(DosDatetime _v) { _dirty = true; _root = _v; }
public DosDatetime _parent() { return _parent; }
public void set_parent(DosDatetime _v) { _dirty = true; _parent = _v; }
}
private Time time;
private Date date;
private DosDatetime _root;
private KaitaiStruct.ReadWrite _parent;
public Time time() { return time; }
public void setTime(Time _v) { _dirty = true; time = _v; }
public Date date() { return date; }
public void setDate(Date _v) { _dirty = true; date = _v; }
public DosDatetime _root() { return _root; }
public void set_root(DosDatetime _v) { _dirty = true; _root = _v; }
public KaitaiStruct.ReadWrite _parent() { return _parent; }
public void set_parent(KaitaiStruct.ReadWrite _v) { _dirty = true; _parent = _v; }
}