Date/Time/Number Formatting

1
Date/Time/Number Formatting

• Alan Liu
• Globalization Center of Competency
• IBM Emerging Technology Center

2

• Overview

3
The Problem

• Display a date in different languages
• English Friday, June 4, 1999
• German Freitag, 4. Juni 1999
• French vendredi 4 juin 1999

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The Problem

• Display a date in different languages
• Convert a time between local time zones
• Los Angeles June 3, 1999 500 PM PDT
• New York June 3, 1999 800 PM EDT
• Paris June 4, 1999 200 AM CEST

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The Problem

• Display a date in different languages
• Convert a time between local time zones
• Handle daylight savings time
• Sat. Oct. 28, 2000 300 PM PDT 24 hours
• Sun. Oct. 29, 2000 200 PM PST

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The Problem

• These problems boil down to
• Formatting
• Parsing
• Data conversion
• These operations apply to different data types
• Dates and times
• Numbers, including currency amounts
• Messages

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Formatting and Parsing

• Formatting conversion of binary data to text
• Parsing conversion of text to binary data
• Different locales use different text to represent
  the same piece of binary data

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Data Conversion

• In different locales, not only the form but also
  the value of displayed data may change
• Reflects different local conventions time zone,
  definition of the week, calendar
• Applies only to dates and times

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Data Conversion

• Displayed data values differ depending on the
  locale
• Underlying binary data does not change
• Displayed data Calendar fields
• Underlying data UDate scalar

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Data Conversion

• Conversion happens implicitly during formatting
  and parsing
• Conversion can also be done explicitly

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• Date and Time

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Date and Time

• Date and time stored together as a scalar
• Resolution of 1 millisecond
• Range roughly 70,000 BC to 70,000 AD
• Stored as absolute time independent of local time
  zones (GMT-based)

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Date and Time

• Extensible calendar system
• Rule-based time zones with built-in data for all
  modern international zones (over 400)
• Rule-based date format with built-in data for
  many locales (over 140)

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Date and Time Components

• UDate GMT-based date and time (ms)
• Calendar Convert UDate to/from fields
• TimeZone Convert GMT to/from local zone
• DateFormat Convert UDate to/from text

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Date and Time Components

• Fit together in a specific nested pattern

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Date and Time Components

• Fit together in a specific nested pattern
• Create
• TimeZone object zone
• Calendar object cal
• DateFormat object fmt
• Set cals time zone to zone
• Set fmts calendar to cal

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Date and Time Components

• If components are not nested explicitly, then
  they use default objects, which can lead to
  errors
• DateFormat uses a default Calendar
• Calendar uses a default TimeZone

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Calendar Two Roles

• Always set to a specific UDate
• Converts UDate to/from fields
• Fields are integer values for the month, day,
  year, hour, minutes, day of week, etc.
• See calendar.h for complete field list

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Detail Calendar Fields

• Conversion of fields to UDatecal.clear()cal.se
  t(YEAR, 1999)cal.set(MONTH, JUNE)cal.set(DAY_O
  F_WEEK, MONDAY)cal.set(WEEK_OF_MONTH, 2)UDate
  d cal.getTime()

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Detail Calendar Fields

• Conversion of UDate to fields cal.setTime(myUDat
  e)int32_t month cal.get(MONTH)

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Time Zones

• Standard Olson (UNIX) time zone data
• Over 400 international time zones
• Does not rely on host OS
• No historical time zone support
• Time zones always used with calendars

22
Formatters Code Patterns

• Code contains generic pattern engine
• Locale resources contain different patterns
• Different groups of patterns for different
  locales
• Within each group, different patterns for
  different variants e.g., one for Wed 6 Sep 00
  and another for Wednesday 7 September 2000

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Formatter Types

• DateFormat already discussed
• NumberFormat handles 1,234.56
• MessageFormat handles 3 Files Found
• ChoiceFormat handles no files/one file

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Formatters Pattern Syntax

• Each formatter supports its own pattern syntax
• For number and date formats, most users can use
  locale data
• For message format, users will have to write
  their own patterns
• See headers for pattern syntax documentation

25
Future Directions

• Support for time zone aliasing
• Support for traditional calendar systems
• Support for rule-based number formatting (e.g.,
  three hundred and sixty-four)

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Exercises

• Exercise 1 datefmt
• Use DateFormat to format a date and time into
  several localized strings
• Convert the date and time into local time zones

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Exercises

• Exercise 2 msgfmt
• Use MessageFormat to format a number and date
• Use a ChoiceFormat pattern to format the number
  idiomatically