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.
All parsing code for Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.
The Python runtime library can be installed from PyPI:
python3 -m pip install kaitaistructParse a local file and get structure in memory:
data = DosDatetime.from_file("path/to/local/file.bin")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = DosDatetime(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.time # => get time
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 9):
raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))
class DosDatetime(KaitaiStruct):
"""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)
.. seealso::
Source - https://learn.microsoft.com/en-us/windows/win32/sysinfo/ms-dos-date-and-time
.. seealso::
Source - https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-dosdatetimetofiletime
.. seealso::
DosDateTimeToFileTime - https://github.com/reactos/reactos/blob/c6b64448ce4/dll/win32/kernel32/client/time.c#L82-L87
.. seealso::
page 25/34 - https://download.microsoft.com/download/0/8/4/084c452b-b772-4fe5-89bb-a0cbf082286a/fatgen103.doc
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.time = DosDatetime.Time(self._io, self, self._root)
self.date = DosDatetime.Date(self._io, self, self._root)
class Time(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.second_div_2 = self._io.read_bits_int_le(5)
if not self.second_div_2 <= 29:
raise kaitaistruct.ValidationGreaterThanError(29, self.second_div_2, self._io, u"/types/time/seq/0")
self.minute = self._io.read_bits_int_le(6)
if not self.minute <= 59:
raise kaitaistruct.ValidationGreaterThanError(59, self.minute, self._io, u"/types/time/seq/1")
self.hour = self._io.read_bits_int_le(5)
if not self.hour <= 23:
raise kaitaistruct.ValidationGreaterThanError(23, self.hour, self._io, u"/types/time/seq/2")
@property
def second(self):
if hasattr(self, '_m_second'):
return self._m_second
self._m_second = (2 * self.second_div_2)
return getattr(self, '_m_second', None)
@property
def padded_second(self):
if hasattr(self, '_m_padded_second'):
return self._m_padded_second
self._m_padded_second = (u"0" if self.second <= 9 else u"") + str(self.second)
return getattr(self, '_m_padded_second', None)
@property
def padded_minute(self):
if hasattr(self, '_m_padded_minute'):
return self._m_padded_minute
self._m_padded_minute = (u"0" if self.minute <= 9 else u"") + str(self.minute)
return getattr(self, '_m_padded_minute', None)
@property
def padded_hour(self):
if hasattr(self, '_m_padded_hour'):
return self._m_padded_hour
self._m_padded_hour = (u"0" if self.hour <= 9 else u"") + str(self.hour)
return getattr(self, '_m_padded_hour', None)
class Date(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.day = self._io.read_bits_int_le(5)
if not self.day >= 1:
raise kaitaistruct.ValidationLessThanError(1, self.day, self._io, u"/types/date/seq/0")
self.month = self._io.read_bits_int_le(4)
if not self.month >= 1:
raise kaitaistruct.ValidationLessThanError(1, self.month, self._io, u"/types/date/seq/1")
if not self.month <= 12:
raise kaitaistruct.ValidationGreaterThanError(12, self.month, self._io, u"/types/date/seq/1")
self.year_minus_1980 = self._io.read_bits_int_le(7)
@property
def year(self):
"""only years from 1980 to 2107 (1980 + 127) can be represented."""
if hasattr(self, '_m_year'):
return self._m_year
self._m_year = (1980 + self.year_minus_1980)
return getattr(self, '_m_year', None)
@property
def padded_day(self):
if hasattr(self, '_m_padded_day'):
return self._m_padded_day
self._m_padded_day = (u"0" if self.day <= 9 else u"") + str(self.day)
return getattr(self, '_m_padded_day', None)
@property
def padded_month(self):
if hasattr(self, '_m_padded_month'):
return self._m_padded_month
self._m_padded_month = (u"0" if self.month <= 9 else u"") + str(self.month)
return getattr(self, '_m_padded_month', None)
@property
def padded_year(self):
if hasattr(self, '_m_padded_year'):
return self._m_padded_year
self._m_padded_year = (u"0" + (u"0" + (u"0" if self.year <= 9 else u"") if self.year <= 99 else u"") if self.year <= 999 else u"") + str(self.year)
return getattr(self, '_m_padded_year', None)