# DateTime

  Encapsulation of date/time values

# Module Functions

Timezones()

  Return the list of recognized timezone names

# Class DateTime

DateTime objects represent instants in time and provide interfaces for controlling its representation without affecting the absolute value of the object.

DateTime objects may be created from a wide variety of string or numeric data, or may be computed from other DateTime objects. DateTimes support the ability to convert their representations to many major timezones, as well as the ablility to create a DateTime object in the context of a given timezone.

DateTime objects provide partial numerical behavior:

- Two date-time objects can be subtracted to obtain a time, in days between the two.

- A date-time object and a positive or negative number may be added to obtain a new date-time object that is the given number of days later than the input date-time object.

- A positive or negative number and a date-time object may be added to obtain a new date-time object that is the given number of days later than the input date-time object.

- A positive or negative number may be subtracted from a date-time object to obtain a new date-time object that is the given number of days earlier than the input date-time object.

DateTime objects may be converted to integer, long, or float numbers of days since January 1, 1901, using the standard int, long, and float functions (Compatibility Note: int, long and float return the number of days since 1901 in GMT rather than local machine timezone). DateTime objects also provide access to their value in a float format usable with the python time module, provided that the value of the object falls in the range of the epoch-based time module.

A DateTime object should be considered immutable; all conversion and numeric operations return a new DateTime object rather than modify the current object.

Constructor For DateTime

  DateTime()

    ### Return a new date-time object

    A DateTime object always maintains its value as an absolute UTC time, and is represented in the context of some timezone based on the arguments used to create the object. A DateTime object's methods return values based on the timezone context.

    Note that in all cases the local machine timezone is used for representation if no timezone is specified.

    #### DateTimes may be created with from zero to seven arguments.

    - If the function is called with no arguments, then the current date/time is returned, represented in the timezone of the local machine.

    - If the function is invoked with a single string argument which is a recognized timezone name, an object representing the current time is returned, represented in the specified timezone.

    - If the function is invoked with a single string argument representing a valid date/time, an object representing that date/time will be returned.

      As a general rule, any date-time representation that is recognized and unambigous to a resident of North America is acceptable.(The reason for this qualification is that in North America, a date like: 2/1/1994 is interpreted as February 1, 1994, while in some parts of the world, it is interpreted as January 2, 1994.) A date/time string consists of two components, a date component and an optional time component, separated by one or more spaces. If the time component is omited, 12:00am is assumed. Any recognized timezone name specified as the final element of the date/time string will be used for computing the date/time value. (If you create a DateTime with the string `Mar 9, 1997 1:45pm US/Pacific`, the value will essentially be the same as if you had captured time.time() at the specified date and time on a machine in that timezone)

                      e=DateTime(US/Eastern)
                      # returns current date/time, represented in US/Eastern.

                      x=DateTime(1997/3/9 1:45pm)
                      # returns specified time, represented in local machine zone.

                      y=DateTime(Mar 9, 1997 13:45:00)
                      # y is equal to x

      The date component consists of year, month, and day values. The year value must be a one-, two-, or four-digit integer. If a one- or two-digit year is used, the year is assumed to be in the twentieth century. The month may an integer, from 1 to 12, a month name, or a month abreviation, where a period may optionally follow the abreviation. The day must be an integer from 1 to the number of days in the month. The year, month, and day values may be separated by periods, hyphens, forward, shashes, or spaces. Extra spaces are permitted around the delimiters. Year, month, and day values may be given in any order as long as it is possible to distinguish the components. If all three components are numbers that are less than 13, then a a month-day-year ordering is assumed.

      The time component consists of hour, minute, and second values separated by colons. The hour value must be an integer between 0 and 23 inclusively. The minute value must be an integer between 0 and 59 inclusively. The second value may be an integer value between 0 and 59.999 inclusively. The second value or both the minute and second values may be ommitted. The time may be followed by am or pm in upper or lower case, in which case a 12-hour clock is assumed.

    - If the DateTime function is invoked with a single Numeric argument, the number is assumed to be either a floating point value such as that returned by time.time() , or a number of days after January 1, 1901 00:00:00 UTC.

      A DateTime object is returned that represents either the gmt value of the time.time() float represented in the local machine's timezone, or that number of days after January 1, 1901. Note that the number of days after 1901 need to be expressed from the viewpoint of the local machine's timezone. A negative argument will yield a date-time value before 1901.

    - If the function is invoked with two numeric arguments, then the first is taken to be an integer year and the second argument is taken to be an offset in days from the beginning of the year, in the context of the local machine timezone. The date-time value returned is the given offset number of days from the beginning of the given year, represented in the timezone of the local machine. The offset may be positive or negative. Two-digit years are assumed to be in the twentieth century.

    - If the function is invoked with two arguments, the first a float representing a number of seconds past the epoch in gmt (such as those returned by time.time()) and the second a string naming a recognized timezone, a DateTime with a value of that gmt time will be returned, represented in the given timezone.

                      import time
                      t=time.time()
                      now_east=DateTime(t,'US/Eastern')
                      # Time t represented as US/Eastern

                      now_west=DateTime(t,'US/Pacific')
                      # Time t represented as US/Pacific

                      # now_east == now_west
                      # only their representations are different

    - If the function is invoked with three or more numeric arguments, then the first is taken to be an integer year, the second is taken to be an integer month, and the third is taken to be an integer day. If the combination of values is not valid, then a DateTimeError is raised. Two-digit years are assumed to be in the twentieth century. The fourth, fifth, and sixth arguments are floating point, positive or negative offsets in units of hours, minutes, and days, and default to zero if not given. An optional string may be given as the final argument to indicate timezone (the effect of this is as if you had taken the value of time.time() at that time on a machine in the specified timezone).

    If a string argument passed to the DateTime constructor cannot be parsed, it will raise DateTime.SyntaxError. Invalid date, time, or timezone components will raise a DateTime.DateTimeError.

    The module function Timezones() will return a list of the timezones recognized by the DateTime module. Recognition of timezone names is case-insensitive.

Instance Methods For DateTime

  aMonth()

    Return the abreviated month name.

  pCommon()

    Return a string representing the object's value in the format: Mar. 1, 1997 1:45 pm

  minute()

    Return the minute

  isLeapYear()

    Return true if the current year (in the context of the object's timezone) is a leap year

  pMonth()

    Return the abreviated (with period) month name.

  DayOfWeek()

    Compatibility: see Day

  Day_()

    Compatibility: see pDay

  isCurrentDay()

    Return true if this object represents a date/time that falls within the current day, in the context of this object's timezone representation

  Mon()

    Compatibility: see aMonth

  hour()

    Return the 24-hour clock representation of the hour

  Date()

    Return the date string for the object.

  aCommonZ()

    Return a string representing the object's value in the format: Mar 1, 1997 1:45 pm US/Eastern

  fCommonZ()

    Return a string representing the object's value in the format: March 1, 1997 1:45 pm US/Eastern

  isCurrentYear()

    Return true if this object represents a date/time that falls within the current year, in the context of this object's timezone representation

  AMPMMinutes()

    Return the time string for an object not showing seconds.

  dd()

    Return day as a 2 digit string

  TimeMinutes()

    Return the time string for an object not showing seconds.

  h_24()

    Return the 24-hour clock representation of the hour

  isPast()

    Return true if this object represents a date/time earlier than the time of the call

  dow()

    Return the integer day of the week, where sunday is 0

  isFuture()

    Return true if this object represents a date/time later than the time of the call

  pCommonZ()

    Return a string representing the object's value in the format: Mar. 1, 1997 1:45 pm US/Eastern

  timezone()

    Return the timezone in which the object is represented.

  h_12()

    Return the 12-hour clock representation of the hour

  PreciseTime()

    Return the time string for the object.

  isCurrentMinute()

    Return true if this object represents a date/time that falls within the current minute, in the context of this object's timezone representation

  rfc822()

    Return the date in RFC 822 format

  equalTo(t)

    Compare this DateTime object to another DateTime object OR a floating point number such as that which is returned by the python time module. Returns true if the object represents a date/time equal to the specified DateTime or time module style time.

  yy()

    Return calendar year as a 2 digit string

  mm()

    Return month as a 2 digit string

  Mon_()

    Compatibility: see pMonth

  toZone(z)

    Return a DateTime with the value as the current object, represented in the indicated timezone.

  earliestTime()

    Return a new DateTime object that represents the earliest possible time (in whole seconds) that still falls within the current object's day, in the object's timezone context

  aDay()

    Return the abreviated name of the day of the week

  dayOfYear()

    Return the day of the year, in context of the timezone representation of the object

  latestTime()

    Return a new DateTime object that represents the latest possible time (in whole seconds) that still falls within the current object's day, in the object's timezone context

  notEqualTo(t)

    Compare this DateTime object to another DateTime object OR a floating point number such as that which is returned by the python time module. Returns true if the object represents a date/time not equal to the specified DateTime or time module style time.

  PreciseAMPM()

    Return the time string for the object.

  day()

    Return the integer day

  timeTime()

    Return the date/time as a floating-point number in UTC, in the format used by the python time module. Note that it is possible to create date/time values with DateTime that have no meaningful value to the time module, and in such cases a DateTimeError is raised. A DateTime object's value must generally be between Jan 1, 1970 (or your local machine epoch) and Jan 2038 to produce a valid time.time() style value.

  ampm()

    Return the appropriate time modifier (am or pm)

  greaterThan(t)

    Compare this DateTime object to another DateTime object OR a floating point number such as that which is returned by the python time module. Returns true if the object represents a date/time greater than the specified DateTime or time module style time.

  month()

    Return the month of the object as an integer

  AMPM()

    Return the time string for an object to the nearest second.

  second()

    Return the second

  parts()

    Return a tuple containing the calendar year, month, day, hour, minute second and timezone of the object

  greaterThanEqualTo(t)

    Compare this DateTime object to another DateTime object OR a floating point number such as that which is returned by the python time module. Returns true if the object represents a date/time greater than or equal to the specified DateTime or time module style time.

  lessThanEqualTo(t)

    Compare this DateTime object to another DateTime object OR a floating point number such as that which is returned by the python time module. Returns true if the object represents a date/time less than or equal to the specified DateTime or time module style time.

  isCurrentHour()

    Return true if this object represents a date/time that falls within the current hour, in the context of this object's timezone representation

  aCommon()

    Return a string representing the object's value in the format: Mar 1, 1997 1:45 pm

  dow_1()

    Return the integer day of the week, where sunday is 1

  Day()

    Return the full name of the day of the week

  fCommon()

    Return a string representing the object's value in the format: March 1, 1997 1:45 pm

  Month()

    Return the full month name

  isCurrentMonth()

    Return true if this object represents a date/time that falls within the current month, in the context of this object's timezone representation

  year()

    Return the calendar year of the object

  lessThan(t)

    Compare this DateTime object to another DateTime object OR a floating point number such as that which is returned by the python time module. Returns true if the object represents a date/time less than the specified DateTime or time module style time.

  Time()

    Return the time string for an object to the nearest second.

  pDay()

    Return the abreviated (with period) name of the day of the week

General Services Provided by DateTime

  `aDateTime`

    Convert a DateTime to a string that looks like a Python expression.

  str(aDateTime)

    Convert a DateTime to a string.

  cmp(aDateTime, other)

    Compare a DateTime with another DateTime object, or a float such as those returned by time.time().

    NOTE: __cmp__ support is provided for backward compatibility only, and mixing DateTimes with ExtensionClasses could cause __cmp__ to break. You should use the methods lessThan, greaterThan, lessThanEqualTo, greaterThanEqualTo, equalTo and notEqualTo to avoid potential problems later!!

  hash(aDateTime)

    Compute a hash value for a DateTime

Numeric Services Provided by DateTime

  aDateTime + other

    A DateTime may be added to a number and a number may be added to a DateTime; two DateTimes cannot be added.

  aDateTime - other

    Either a DateTime or a number may be subtracted from a DateTime, however, a DateTime may not be subtracted from a number.

  other + aDateTimeAdd aDateTime to other.

    A DateTime may be added to a number and a number may be added to a DateTime; two DateTimes cannot be added.

  int(aDateTime)

    Convert to an integer number of days since Jan. 1, 1901 (gmt)

  long(aDateTime)

    Convert to a long-int number of days since Jan. 1, 1901 (gmt)

  float(aDateTime)

    Convert to floating-point number of days since Jan. 1, 1901 (gmt)

Last Modified: 14 March 1997