Eve Date and Time

Calendar Date

In Eve, we represent calendar dates using a Date object that contains four fields: era, year, month, day.

Date Structure

The Date type is defined as an object with the following fields:

• era: Ordinal {BCE, CE}, the default is CE
• year: Integer representing the year, 1 or more (there is no year 0)
• month: Integer representing the month (1-12)
• day: Integer representing the day of the month (1-31)

Note: Dates before the Common Era have the era BCE. A comparison puts every BCE date before every CE date.

Date Literals

A date is created in two ways: from a string, using the method parse() with a format constant, or from an object literal with a type hint. The format constants are YMD, DMY and MDY:

• YMD format: "YYYY/MM/DD"
• DMY format: "DD/MM/YYYY"
• MDY format: "MM/DD/YYYY"

Note: A string may end with an era label: CE, AD, BCE or BC. If it is omitted, the era is CE.

Example Usage

#date format demo
driver date_demo is

  process main is
    new date1 := "2023/06/15".parse(YMD);       ** June 15, 2023 CE
    new date2 := "30/11/753 BCE".parse(DMY);    ** November 30, 753 BCE
    new date3 := "07/04/1776 AD".parse(MDY);    ** July 4, 1776 AD
    new date4 := "01/01/2000".parse(DMY);       ** January 1, 2000 CE

    ** Date comparisons
    expect date3 > date2;  ** 1776 AD is after 753 BCE
    expect date1 > date3;  ** 2023 CE is after 1776 AD
    expect date4 > date3;  ** 2000 is after 1776

    ** Access individual fields
    print "Year of date1: {date1.year}";
    print "Month of date2: {date2.month}";
    print "Era of date2: {date2.era}";

    ** Create a new date
    new custom_date = {era: CE, year: 1066, month: 10, day: 14} :Date;
    print custom_date; ** {era: CE, year: 1066, month: 10, day: 14}

    ** Format a date for printing (one direction)
    print date1 as YMD; ** 2023/06/15
  return;
end date_demo;

Additional Methods

The Date object provides various methods for manipulation and querying:

• is_bce(): Returns True if the era is BCE, False otherwise
• to_julian(): Converts the date to Julian Day Number
• from_julian(jdn): Creates a date from a Julian Day Number
• add_days(n): Returns a new Date object n days after this date
• subtract_days(n): Returns a new Date object n days before this date
• days_between(other_date): Calculates days between two dates

Time & Duration

We use Time or Duration data types. These are primitive types not nullable.

Time

A Time is created from a string using the method parse() with a format constant. The constants T12 and T24 represent the standard time formats:

• Constant: T12 = "hh:mm:ssxx, 999ms"
• Constant: T24 = "hh:mm:ss, 999ms"

hh: hours, 00..23 in T24 and 01..12 in T12
mm: minutes, 00..59
ss: seconds, 00..59
xx: can be: (am/pm)
999ms: milliseconds

Example:

# time demo
driver time_demo is

  process main is
    ** define 3 variable of same type
    new time1, time2, time3 :Time;

    ** alter variables using method parse(), the format is expected
    let time1 := "00:23:59, 0ms".parse(T24);
    new time2 := "23:59:59, 999ms".parse(T24);
    new time3 := "11:59:59pm, 10ms".parse(T12);

    ** check time
    expect time1.h   == 0;
    expect time1.m   == 23;
    expect time1.s   == 59;
    expect time2.ms  == 999;
    expect time3.ms  == 10;
    expect time3.t   == pm;
  return;
end time_demo;

Duration

Duration is an object with the fields year, days, hours, min, sec and ms. Internally it is stored as a signed 64-bit number of milliseconds. The field min means minutes: the name is written in full to avoid confusion with months.

• A Duration literal is an object literal: {year:34, days:365, hours:4, min:30, sec:26, ms:444}.
• The fields you omit are zero.
• The range is -2^63 .. 2^63-1 milliseconds.

Example

# duration demo
driver duration_demo is

  process main is
    ** define 3 variable of same type
    new d1 = {ms: 10}  :Duration;   **    10 millisec
    new d2 = {sec: 1}  :Duration;   **  1000 millisec
    new d3 = {min: 1}  :Duration;   ** 60000 millisec

    ** create duration from string
    new d4 := Duration("01:01:01");

    ** check time
    print d3; ** 60000ms
    print d4; ** 3661000ms
  return;
end duration_demo;

Quick Format

For printing output using a format we use operator as that is the "quick format" operator. We can use system constant templates that are available for making different formats for different data types. For other values use string interpolation ({name % format}).

The operator as works in one direction only: it formats a value into a string. The other direction is a method of String: "15:30:00, 0ms".parse(T24). The argument of parse() is the format that is expected.

Date Format

Eve has constants to define the date format:

Time Format

Eve has constants to define the time format:

Numeric Format

Eve can print comma "," for decimal numbers but also can print dot.

Read next: Control Flow