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# file openpyxl/shared/date_time.py
# Copyright (c) 2010 openpyxl
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
# @license: http://www.opensource.org/licenses/mit-license.php
# @author: Eric Gazoni
"""Manage Excel date weirdness."""
# Python stdlib imports
from math import floor
import calendar
import datetime
import time
import re
# constants
W3CDTF_FORMAT = '%Y-%m-%dT%H:%M:%SZ'
RE_W3CDTF = '(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})(.(\d{2}))?Z'
EPOCH = datetime.datetime.utcfromtimestamp(0)
def datetime_to_W3CDTF(dt):
"""Convert from a datetime to a timestamp string."""
return datetime.datetime.strftime(dt, W3CDTF_FORMAT)
def W3CDTF_to_datetime(formatted_string):
"""Convert from a timestamp string to a datetime object."""
match = re.match(RE_W3CDTF,formatted_string)
digits = list(map(int, match.groups()[:6]))
return datetime.datetime(*digits)
class SharedDate(object):
"""Date formatting utilities for Excel with shared state.
Excel has a two primary date tracking schemes:
Windows - Day 1 == 1900-01-01
Mac - Day 1 == 1904-01-01
SharedDate stores which system we are using and converts dates between
Python and Excel accordingly.
"""
CALENDAR_WINDOWS_1900 = 1900
CALENDAR_MAC_1904 = 1904
datetime_object_type = 'DateTime'
def __init__(self):
self.excel_base_date = self.CALENDAR_WINDOWS_1900
def datetime_to_julian(self, date):
"""Convert from python datetime to excel julian date representation."""
if isinstance(date, datetime.datetime):
return self.to_julian(date.year, date.month, date.day, \
hours=date.hour, minutes=date.minute, seconds=date.second)
elif isinstance(date, datetime.date):
return self.to_julian(date.year, date.month, date.day)
def to_julian(self, year, month, day, hours=0, minutes=0, seconds=0):
"""Convert from Python date to Excel JD."""
# explicitly disallow bad years
# Excel 2000 treats JD=0 as 1/0/1900 (buggy, disallow)
# Excel 2000 treats JD=2958466 as a bad date (Y10K bug!)
if year < 1900 or year > 10000:
msg = 'Year not supported by Excel: %s' % year
raise ValueError(msg)
if self.excel_base_date == self.CALENDAR_WINDOWS_1900:
# Fudge factor for the erroneous fact that the year 1900 is
# treated as a Leap Year in MS Excel. This affects every date
# following 28th February 1900
if year == 1900 and month <= 2:
excel_1900_leap_year = False
else:
excel_1900_leap_year = True
excel_base_date = 2415020
else:
raise NotImplementedError('Mac dates are not yet supported.')
#excel_base_date = 2416481
#excel_1900_leap_year = False
# Julian base date adjustment
if month > 2:
month = month - 3
else:
month = month + 9
year -= 1
# Calculate the Julian Date, then subtract the Excel base date
# JD 2415020 = 31 - Dec - 1899 -> Excel Date of 0
century, decade = int(str(year)[:2]), int(str(year)[2:])
excel_date = floor(146097 * century / 4) + \
floor((1461 * decade) / 4) + floor((153 * month + 2) / 5) + \
day + 1721119 - excel_base_date
if excel_1900_leap_year:
excel_date += 1
# check to ensure that we exclude 2/29/1900 as a possible value
if self.excel_base_date == self.CALENDAR_WINDOWS_1900 \
and excel_date == 60:
msg = 'Error: Excel believes 1900 was a leap year'
raise ValueError(msg)
excel_time = ((hours * 3600) + (minutes * 60) + seconds) / 86400
return excel_date + excel_time
def from_julian(self, value=0):
"""Convert from the Excel JD back to a date"""
if self.excel_base_date == self.CALENDAR_WINDOWS_1900:
excel_base_date = 25569
if value < 60:
excel_base_date -= 1
elif value == 60:
msg = 'Error: Excel believes 1900 was a leap year'
raise ValueError(msg)
else:
raise NotImplementedError('Mac dates are not yet supported.')
#excel_base_date = 24107
if value >= 1:
utc_days = value - excel_base_date
return EPOCH + datetime.timedelta(days=utc_days)
elif value >= 0:
hours = floor(value * 24)
mins = floor(value * 24 * 60) - floor(hours * 60)
secs = floor(value * 24 * 60 * 60) - floor(hours * 60 * 60) - \
floor(mins * 60)
return datetime.time(int(hours), int(mins), int(secs))
else:
msg = 'Negative dates (%s) are not supported' % value
raise ValueError(msg)
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