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9067 :: Times - Intended use and difference between DateTime and Time

• volodymyr (orginal) [2022-04-02T11:17:17+02:00] view original

  Hi,

  I'm trying to understand the correct use of the std/times library. Specifically I'd like to know the intended use of the DateTime vs Time.

  A DateTime has all extractors and can be converted to a Time, while a Time has no extractors, but the arithmetic and comparison operations particularly with a Duration are much faster as mentioned in the documentation. Behind the format(Time): string => parse(string): DateTime there is no simple way to convert a DateTime to a Time. It seems that once you use a Time there is no simple way to extract components or convert it to a DateTime, only format(Time) output routine is available.

  Questions

  • What is the correct intended use for a DateTime and a Time? Which one should be used by default in most cases? I guess it should be a DateTime
  • Why there is no simple way to convert a Time to a DateTime? What are the most typical use cases for a Time? I guess a time should be used for UNIX epoch management and efficient arithmetic/comparison operations when no Time components extraction is needed
  • Why the parse(): DateTime supports locale while the parseTime(): Time does not supports locale? Is it intended or the locale support can be added to the parseTime()?

  For your convenience I provide below brief outline of the supported operations by the DateTime and Time types.

  DateTime

  
  # DateTime = time parts
  #   - now(), dateTime() constructors
  #   - [nanosecond..year] extractors
  #   - toTime() DateTime => Time convertor
  #   - parse() + format()
  Run

  Time

  
  # Time = seconds + nanoseconds
  #   - getTime(), initTime() constructors
  #   - NO extractors
  #   - toUnix(), fromUnix() convertors
  #   - parseTime() + format()
  Run

  Arithmetic and comparison

  
  # Arithmetic: DateTime/Time +/- Duration/TimeInterval
  # Comparison: DateTime/Time </<=/== DateTime/Time
  Run

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• Symb0lica (orginal) [2022-04-02T22:05:28+02:00] view original

  As I understand it, the main differences between DateTime and Time are support for timezones and relative efficiencies in addition/subtraction compared to extracting date and time components. If you need to support multiple time zones or expect to issue more calls to extract components than addition/subtractions, choose DateTime, otherwise choose Time.

  For conversion from Time to DateTime, you have local(dt:DateTime) and utc(dt:DateTime).

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• volodymyr (orginal) [2022-04-03T11:06:47+02:00] view original

  Thank you, @Symb0lica, for your advice! It makes complete sense to me! Finally I found the Time => DateTime conversion via inZone(), local(), and utc() functions. Defaulting to Time is reasonable as well. Thank you!

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