A small (≈1kb gzipped), zero-dependency, easy-to-use library for dealing with dates. Only dates. Not times. Not timezones. Just dates.
Your application deals with dates, but doesn't care about times or timezones. You want to add, subtract, compare, and display dates without worrying about where your users are or at what time your date-centric data models get created or read.
E.g. Peter's birthday is on 2012-03-19, no matter when or where you are.
The Dateo class constructor expects an ISO-formatted date string to set a specific date. You can always use the dateo() convenience function to generate
new Dateo instances:
const date = new Dateo('2019-03-12')
// or equivalently
const date = dateo('2019-03-12')Or leaving the constructor blank creates a new dateo instance with today's (via the caller's system) date:
const date = new Dateo()
// or equivalently
const date = dateo()With that dateo instance you can add or subtract days, weeks, months, or years. Dateo objects are immutable, so all instance methods return a new instance with the specified modifations.
The signature for add and subtract is the same: (quantity, unit), where quantity is an integer and unit is a single-character string, 'd', 'w', 'm', or 'y'.
const date = dateo('2019-03-12')
const newDate = date.add(3, 'd')
console.log(newDate.toString()) // '2019-03-15'
const aWeekLater = date.add(1, 'w')
console.log(aWeekLater.toString()) // '2019-03-22'
const aMonthEarlier = aWeekLater.subtract(1, 'm')
console.log(aMonthEarlier.toString()) // '2019-02-22'
const twoYearsHence = aMonthEarlier.add(2, 'y')
console.log(twoYearsHence.toString()) // '2021-02-22'You can also get the start or end of a given time period for a date. You can specify units of 'w', 'm', or 'y'. Dateo considers Sunday to be the week's start, and Saturday to be the week's end.
For example, you might want to know what date was the start of a given dates week:
const date = dateo('2019-03-12')
const weekStart = date.startOf('w')
console.log(weekStart.toString()) // '2019-03-10'
const weekEnd = date.endOf('w')
console.log(weekEnd.toString()) // '2019-03-16'A common situation is the need to compare two dates to know if one date is before, after, or the same as another.
The isBefore, isAfter, and isSame methods all have the same signature, taking another Dateo instance as their only argument, and all either return true or false.
const date = dateo('2019-03-12')
const aLaterDate = dateo('2019-03-13')
console.log(date.isBefore(aLaterDate)) // true
const anEarlierDate = dateo('2019-03-11')
console.log(date.isBefore(anEarlierDate)) // falseFinally, you can format your date using some familiar formatting strings.
const date = dateo('2019-03-05')
console.log(date.format()) // '2019-03-05'
console.log(date.format('YY')) // '19'
console.log(date.format('YYYY')) // '2019'
console.log(date.format('M')) // '3'
console.log(date.format('MM')) // '03'
console.log(date.format('MMM')) // 'Mar'
console.log(date.format('MMMM')) // 'March'
console.log(date.format('D')) // '5'
console.log(date.format('DD')) // '05'
console.log(date.format('d')) // '2' (this is the day of the week, 0-6)
console.log(date.format('dd')) // 'Tu'
console.log(date.format('ddd')) // 'Tue'
console.log(date.format('dddd')) // 'Tuesday'
console.log(date.format('MMM D')) // 'Mar 5'
console.log(date.format('MM/DD/YYYY')) // '03/05/2019'
console.log(date.format('[MM] MM/DD/YYYY')) // 'MM 03/05/2019' (brackets escape formatting strings)The toString method outputs the ISO date string (YYYY-MM-DD).
const date = dateo('2019-03-05')
console.log(date.toString()) // '2019-03-05'
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