Mastering JavaScript Temporal Duration Arithmetic: A Global Guide to Time Interval Mathematics

            const twoYearsThreeMonths = Temporal.Duration.from({
  years: 2,
  months: 3
});

console.log(twoYearsThreeMonths);
// Temporal.Duration { years: 2, months: 3, ... }

const oneDayEightHours = Temporal.Duration.from({
  days: 1,
  hours: 8,
  minutes: 30
});

console.log(oneDayEightHours);
// Temporal.Duration { days: 1, hours: 8, minutes: 30, ... }

const negativeDuration = Temporal.Duration.from({
  hours: -5,
  minutes: -15
});

console.log(negativeDuration);
// Temporal.Duration { hours: -5, minutes: -15, ... }

            

              
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            const isoDuration1 = Temporal.Duration.from('P1Y2M3DT4H5M6S');
console.log(isoDuration1);
// Temporal.Duration { years: 1, months: 2, days: 3, hours: 4, minutes: 5, seconds: 6, ... }

const isoDuration2 = Temporal.Duration.from('P10DT5H'); // 10 days, 5 hours
console.log(isoDuration2);
// Temporal.Duration { days: 10, hours: 5, ... }

const isoDuration3 = Temporal.Duration.from('P3M'); // 3 months
console.log(isoDuration3);
// Temporal.Duration { months: 3, ... }

// Invalid ISO 8601 strings will throw an error.
// Temporal.Duration.from('PT10M5S'); // This is valid
// Temporal.Duration.from('10M'); // This is not valid without 'P'

            

              
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            const constructorDuration = new Temporal.Duration(0, 0, 0, 1, 2, 3); // years, months, weeks, days, hours, minutes
console.log(constructorDuration);
// Temporal.Duration { years: 0, months: 0, weeks: 0, days: 1, hours: 2, minutes: 3, ... }

// Note: The constructor takes arguments in a fixed order (years, months, weeks, days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds).
// Providing fewer arguments means later units are treated as zero.
const partialDuration = new Temporal.Duration(1, 6); // 1 year, 6 months
console.log(partialDuration);
// Temporal.Duration { years: 1, months: 6, ... }

            

              
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            const myDuration = Temporal.Duration.from({
  years: 5,
  days: 10,
  hours: 12,
  minutes: 45
});

console.log(myDuration.years);
// 5
console.log(myDuration.days);
// 10
console.log(myDuration.hours);
// 12
console.log(myDuration.minutes);
// 45
console.log(myDuration.seconds); // Units not specified are 0
// 0

            

              
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            const duration1 = Temporal.Duration.from({ days: 10, hours: 5 });
const duration2 = Temporal.Duration.from({ days: 5, hours: 10 });

const totalDuration = duration1.add(duration2);
console.log(totalDuration);
// Temporal.Duration { days: 15, hours: 15, ... }

const duration3 = Temporal.Duration.from({ years: 1, months: 6 });
const duration4 = Temporal.Duration.from({ months: 8, days: 15 });

const combinedDuration = duration3.add(duration4);
console.log(combinedDuration);
// Temporal.Duration { years: 1, months: 14, days: 15, ... }
// Note: This is a simple aggregation. Temporal will handle unit rollovers (e.g., 14 months becoming 1 year and 2 months) when interacting with PlainDate/Time objects.

// Adding a negative duration is equivalent to subtraction
const duration5 = Temporal.Duration.from({ hours: 3 });
const duration6 = Temporal.Duration.from({ hours: -1 });

const result = duration5.add(duration6);
console.log(result);
// Temporal.Duration { hours: 2, ... }

            

              
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            const durationA = Temporal.Duration.from({ days: 20, hours: 10 });
const durationB = Temporal.Duration.from({ days: 5, hours: 3 });

const remainingDuration = durationA.subtract(durationB);
console.log(remainingDuration);
// Temporal.Duration { days: 15, hours: 7, ... }

// Subtracting a duration that results in a negative value
const durationC = Temporal.Duration.from({ minutes: 30 });
const durationD = Temporal.Duration.from({ minutes: 45 });

const negativeResult = durationC.subtract(durationD);
console.log(negativeResult);
// Temporal.Duration { minutes: -15, ... }

            

              
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            const positiveDuration = Temporal.Duration.from({ hours: 10, minutes: 30 });
const negativeDuration = positiveDuration.negated();
console.log(negativeDuration);
// Temporal.Duration { hours: -10, minutes: -30, ... }

const alreadyNegative = Temporal.Duration.from({ days: -5 });
const nowPositive = alreadyNegative.negated();
console.log(nowPositive);
// Temporal.Duration { days: 5, ... }

            

              
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            const negativeDuration = Temporal.Duration.from({ hours: -8, minutes: -20 });
const absoluteDuration = negativeDuration.abs();
console.log(absoluteDuration);
// Temporal.Duration { hours: 8, minutes: 20, ... }

            

              
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            const dailyDuration = Temporal.Duration.from({ days: 1 });
const twoWeeks = dailyDuration.multiply(14);
console.log(twoWeeks);
// Temporal.Duration { days: 14, ... }

const hourlyIncrement = Temporal.Duration.from({ hours: 1 });
const workWeek = hourlyIncrement.multiply(40);
console.log(workWeek);
// Temporal.Duration { hours: 40, ... }

const projectPhase = Temporal.Duration.from({ months: 2 });
const fullProject = projectPhase.multiply(3);
console.log(fullProject);
// Temporal.Duration { months: 6, ... }

// Multiplication can also be done with negative numbers
const futureEvent = Temporal.Duration.from({ days: 5 }).multiply(-2);
console.log(futureEvent);
// Temporal.Duration { days: -10, ... }

            

              
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            const totalWorkTime = Temporal.Duration.from({ hours: 40, minutes: 30 });
const timePerTask = totalWorkTime.divide(5);
console.log(timePerTask);
// Temporal.Duration { hours: 8, minutes: 1, ... } // 40.5 hours / 5 = 8.1 hours. The 0.1 hours (6 minutes) is truncated.

const projectDuration = Temporal.Duration.from({ days: 90 });
const phaseDuration = projectDuration.divide(3);
console.log(phaseDuration);
// Temporal.Duration { days: 30, ... }

// Dividing by a negative number
const longDuration = Temporal.Duration.from({ years: 2 }).divide(-4);
console.log(longDuration);
// Temporal.Duration { years: -0, ... } // -0.5 years results in 0 years due to truncation.
// For more precise calculations involving division and fractional parts, consider using methods that operate on Temporal.Instant or Temporal.PlainDateTime.

            

              
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            const impreciseDuration = Temporal.Duration.from({
  hours: 2,
  minutes: 35,
  seconds: 45
});

// Round to the nearest minute, using halfExpand (standard rounding)
const roundedToMinute = impreciseDuration.round('minute', Temporal.RoundingMode.halfExpand);
console.log(roundedToMinute);
// Temporal.Duration { hours: 2, minutes: 36, ... } // 35 minutes and 45 seconds rounds up to 36 minutes

// Truncate to the nearest hour
const truncatedToHour = impreciseDuration.round('hour', Temporal.RoundingMode.trunc);
console.log(truncatedToHour);
// Temporal.Duration { hours: 2, ... } // Discards the minutes and seconds.

// Round up to the nearest hour
const ceiledToHour = impreciseDuration.round('hour', Temporal.RoundingMode.ceil);
console.log(ceiledToHour);
// Temporal.Duration { hours: 3, ... } // Since there are minutes and seconds, it rounds up.

// Rounding to a smaller unit (e.g., to seconds) can reveal more precision
const preciseRounding = impreciseDuration.round('second', Temporal.RoundingMode.halfExpand);
console.log(preciseRounding);
// Temporal.Duration { hours: 2, minutes: 35, seconds: 45, ... }

            

              
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            const durationX = Temporal.Duration.from({ days: 1, hours: 12 }); // 1.5 days
const durationY = Temporal.Duration.from({ hours: 36 });     // 1.5 days
const durationZ = Temporal.Duration.from({ days: 2 });       // 2 days

console.log(Temporal.Duration.compare(durationX, durationY)); // 0 (equal)
console.log(Temporal.Duration.compare(durationX, durationZ)); // -1 (durationX is less than durationZ)
console.log(Temporal.Duration.compare(durationZ, durationY)); // 1 (durationZ is greater than durationY)

// Comparison with negative durations
const negDuration1 = Temporal.Duration.from({ hours: -5 });
const negDuration2 = Temporal.Duration.from({ hours: -10 });

console.log(Temporal.Duration.compare(negDuration1, negDuration2)); // 1 (e.g., -5 is greater than -10)

            

              
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            // Example using Temporal.PlainDate (requires polyfill or native support)
// Assuming you have a Temporal polyfill or native support in your environment.

// Let's imagine today is July 15, 2024
const today = Temporal.PlainDate.from({ year: 2024, month: 7, day: 15 });

const durationToAdd = Temporal.Duration.from({ years: 1, months: 3, days: 15 });

const futureDate = today.add(durationToAdd);
console.log(futureDate);
// Temporal.PlainDate { year: 2025, month: 11, day: 1 }

// Global example: Calculating a future date considering different month lengths
const londonDate = Temporal.PlainDate.from({ year: 2024, month: 1, day: 31 }); // January 31st
const durationForNextMonth = Temporal.Duration.from({ months: 1 });

const nextMonthDate = londonDate.add(durationForNextMonth);
console.log(nextMonthDate);
// Temporal.PlainDate { year: 2024, month: 2, day: 29 } // Correctly handles leap year and end of month.

const newYorkDate = Temporal.ZonedDateTime.from({
  timeZone: 'America/New_York',
  year: 2024,
  month: 10,
  day: 28,
  hour: 10,
  minute: 0,
  second: 0
});

const travelDuration = Temporal.Duration.from({ hours: 8 }); // An 8-hour flight

// Note: When adding durations to ZonedDateTime, it's crucial to consider the time zone.
// The result will be in the same time zone unless specified otherwise.
const arrivalTimeNY = newYorkDate.add(travelDuration);
console.log(arrivalTimeNY);
// Temporal.ZonedDateTime { year: 2024, month: 10, day: 28, hour: 18, minute: 0, second: 0, ... }

// If you want to calculate arrival time in a DIFFERENT time zone, you'd typically:
// 1. Add duration to the departure ZonedDateTime.
// 2. Convert the resulting ZonedDateTime to the destination time zone.
const tokyoTimeZone = 'Asia/Tokyo';
const arrivalTimeTokyo = arrivalTimeNY.withTimeZone(tokyoTimeZone);
console.log(arrivalTimeTokyo);
// Temporal.ZonedDateTime { year: 2024, month: 10, day: 29, hour: 7, minute: 0, second: 0, ... } (Note the date and time change due to time zone)

            

              
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            const startDate = Temporal.PlainDate.from({ year: 2023, month: 1, day: 1 });
const endDate = Temporal.PlainDate.from({ year: 2024, month: 3, day: 15 });

const elapsedDuration = startDate.until(endDate);
console.log(elapsedDuration);
// Temporal.Duration { years: 1, months: 2, days: 14, ... }

// Global example: Calculating contract length difference
const contractStart = Temporal.ZonedDateTime.from({
  timeZone: 'UTC',
  year: 2022,
  month: 5,
  day: 10,
  hour: 9,
  minute: 0
});

const contractEnd = Temporal.ZonedDateTime.from({
  timeZone: 'UTC',
  year: 2025,
  month: 8,
  day: 20,
  hour: 17,
  minute: 30
});

const contractLength = contractStart.until(contractEnd);
console.log(contractLength);
// Temporal.Duration { years: 3, months: 3, days: 10, hours: 8, minutes: 30, ... }

// When using until/since with ZonedDateTime, the result can be complex due to time zones and DST.
// Temporal handles this by giving you a duration that may not 'round trip' perfectly if you just add it back without considering the time zone.

            

              
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