date-math

Math. functions for dates

npm install date-math
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date-math

A library to perform mathematical operations on dates. Provides a simple set of functions for working with date ranges, just like you would with Numbers. Uses native UTC APIs rather than simple addition and subtraction, so you can work with dates across timezones.

Quickstart

var Dates = require('date-math');

var now = new Date('2013-10-10T03:45:00Z');

var next = Dates.day.ceil(now); // '2013-10-11T00:00:00.000Z'
var monday = Dates.week.floor(now); // '2013-10-07T00:00:00.000Z'

var future = Dates.month.shift(date, 10); // '2014-08-10T03:45:00.000Z'
var past = Dates.year.shift(date, -10); // '2003-10-10T03:45:00.000Z'

Dates.month.diff(date, future) // 10
Dates.year.diff(date, past); // -10
Dates.month.diff(date, past); // -120

API

The API follows the general format module[timespan]. You can use any of these timespans:

  • second
  • minute
  • hour
  • day
  • week (defaults to ISO week format, starts with monday)
  • month
  • year

    Each timespan has several different methods.

timespan.floor(date)

The equivalent of Math.floor. Returns a new date which is floored to the start of that 'timespan'. If a date is already floored, then an equal date will be returned.

  var now = new Date('2013-10-10T03:45:00Z');
  var lastMonday = Dates.week.floor(now); // '2013-10-07T00:00:00.000Z'
  Dates.week.floor(lastMonday); // '2013-10-07T00:00:00.000Z'
  Dates.day.floor(lastMonday); // '2013-10-07T00:00:00.000Z'
  Dates.day.floor(now); // '2013-10-10T00:00:00.000Z'

timespan.ceil(date)

The equivalent of Math.ceil. Returns a new date which is ceil'd to the start of the next timespan. If a date already is at the start of a timespan, then an equal date will be returned.

  var now = new Date('2013-10-10T03:45:00Z');
  var nextMonday = Dates.week.ceil(now); // '2013-10-14T00:00:00.000Z'
  Dates.week.ceil(nextMonday); // '2013-10-14T00:00:00.000Z'
  Dates.day.ceil(nextMonday); // '2013-10-14T00:00:00.000Z'
  Dates.day.ceil(now); // '2013-10-11T00:00:00Z'

timespan.diff(start, end)

The equivalent of subtracting two numbers, .diff finds the difference between two dates. It returns the whole number amount of timespans which can fit between the two dates.

  var now = new Date('2013-10-10T03:45:00Z');
  Dates.day.diff(now, new Date('2013-10-11T00:00:00Z'); // 0
  Dates.day.diff(now, new Date('2013-10-11T03:45:00Z'); // 1
  Dates.day.diff(now, new Date('2013-10-09T03:45:00Z'); // -1
  Dates.day.diff(now, new Date('2013-10-11T03:46:78Z'); // 1

timespan.shift(date, amount)

Shifts the date by the amount of the timespan. Negative numbers will shift the date into the past.

  var now = new Date('2013-10-10T03:45:00Z');
  Dates.minute.shift(now, 10); // '2013-10-10T03:55:00Z'
  Dates.minute.shift(now, -10); // 2013-10-10T03:35:00Z

License

(The MIT License)

Copyright (c) 2013 segmentio <team@segment.io>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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